British Journal of Dermatology {1976) 94, 473.
Clinical and Laboratory Investigations
The pathology of lymphangioma circumscriptum I.W.WHIMSTER Department of Dermatology, St Thomas' Hospital and Medical School, London SEi
Accepted for publication 30 August 1975
SUMMARY
A Study of lymphangioma circumscriptum has been carried out over a number of years in an attempt to understand its nature and pathogenesis, with a view to improving treatment. It is postulated that the lesion consists essentially of a collection of large muscular-coated lymphatic cisterns, lying deep in the subcutaneous plane and communicating via dilated dermal lymphatics with the superficial vesicles. It seems that these cisterns do not communicate directly, if at all, with the general lymphatic system but represent a sequestrated part of it. They have been shown by cannulation to pulsate at a slow steady rate producing a rise and fall of pressure within them. It is believed that the vesicles are saccular dilatations of superficial lymphatics, secondary to raised pressure transmitted from the pulsating cisterns beneath. It is suggested that it may be possible to treat these lesions more successfully and with better cosmetic results by excising the subcutaneous cisterns and leaving the overlying skin intact.
Lymphangioma circumscriptum (L.C.) is characterized clinically by the presence within a circumscribed area of skin of vesicles, mostly filled with clear colourless fluid but occasionally tinged with varying quantities of blood, the colour then ranging from pink, through red to black. The clinical aspects of the condition were reviewed by Peachey, Lim & Whimstcr in 1970. The present article is concerned entirely with the type of lesion defined by these authors as the 'classical' form (Fig. i).
FIGURE I. A circumscribed group of L.C. vesicles, ranging from colourless to dark red, just above the left iliac crest of a girl of 14 years. They had been present and increasing in numbers since the age of 6 years. Beneath the involved skin there was a deep diffuse subcutaneous swelling. * Extension of a paper presented at the B.A.D. Meeting, London, July 1974. 473
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The condition is usually present at birth or develops soon afterwards, commonly becoming more intense throughout childhood and persisting indefinitely. It is a nuisance to the patient, not only because of the cosmetic disfigurement caused by the presence of the vesicles but also because of their tendency to rupture and leak fluid which stains clothing. While being well known and easily recognized by its clinical manifestations there were two features about the condition which seemed to call for further investigation. First, its pathogenesis was unknown and, secondly, it was apparent that present methods of treatment were profoundly unsatis-
FIGURE 2 (a) Skin from within an area of L.C. but between vesicles. In the upper dermis there are grossly dilated lymphatic vessels orientated mainly in the horizontal plane. (b) Enlarged and dilated muscle-coated lymphatic running vertically in the lower dermis beneath an area of vesicles. (c) An early stage in vesicle formation. The dilated vessels in the photograph can be seen in serial sections to be interconnected. Beneath the epidermis is a very dilated thin walled lymphatic arising from the horizontal vessels as a blind-ended sac. (d) Fully formed L.C. vesicle occupying a whole papilla and arising like a balloon from a horizontal vessel lying just below the papillary layer.
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factory. It was felt that if the pathology of the condition were better understood this might in turn lead to improved methods of therapy. This article is an attempt to set out the progressive series of observations which have been made over a number of years of the morbid anatomy, the histology and the natural history of the condition, together with the sequence of conclusions, hypotheses and further investigations arising out of them. The study has been based mainly on thirty cases from which whole surgical excision specimens were available for dissection and histological examination by the author, backed up by many further cases from which less complete material was available. Observations (1) However large or small the area of skin involved in L.C. may be, it is as the name implies a circumscribed one. The arrangement of herpes zoster lesions within a characteristically circumscribed area of skin, as opposed to the diffuse scattering of varicella lesions, led to the recognition of the reason for this grouping and to the common link between all the lesions of a group; a posterior root ganglion. It was felt that the circumscribed grouping of L.C. vesicles must have a similar significance, in that it indicated the presence of some underlying link between ail the individual and apparently separate vesicles within the circumscribed area. (2) In L.C. the dermis immediately beneath the papillary layer contains dilated thin-walled lymphatics mainly orientated horizontally, and deep to these are others, some with thicker walls, mainly running vertically (Fig. 2a, b). (3) The vesicles of L.C. are saccular dilatations bulging out from thin-walled lymphatics and projecting upwards to occupy the papillae only when sufficiently distended. So far as I have personally been able to convince myself there are no lymphatics in normal dermal papillae (Fig. 2c, d). (4) The vesicles are often not present at birth, and even when some are, others certainly arise later. This suggests that the dilatation of the saccular vessels is not due to any intrinsic fault of the normal
FIGURE 3. (a) A girl aged 9 years with a group of L.C. vesicles on the right shoulder. Two vesicles were present at birth and their number had increased subsequently. (b) The same patient 6 months after excision of almost all the affected skin together with subcutaneous tissue to a total depth of 10 mm. There wore large abnormal lymphatics transected at the base of the excision specimen. At this post-operative stage there are already a few new vesicles forming alongside the scar. (c) The same patient 2 years later. There are now almost as many newly formed vesicles in the area as there were in the original lesion.
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FIGURE 4. (a) Female aged 18 years. A vesicle from an area of typical L.C. The affected skin was excised and the wound repaired with a full thickness pedicle graft. Subsequently the graft developed abundant new vesicles. (b) The same patient as in (a). A vesicle in the graft about 18 months after operation.
dermal lymphatics of the area concerned but that the fault, whatever its nature, is an acquired one, affecting vessels which either appeared normal previously or were not in existence at that time. (5) After excision of lymphangiomatous skin, with the full thickness of dermis and including all the vesicles present, 'recurrence' of vesicles (that is to say the formation of new vesicles) is the rule, whether the wound has been sutured or grafted. This phenomenon indicates that skin whose superficial lymphatics have previously behaved normally can be made to develop saccular ones as a result of its coming to occupy the site of the original lesion. Fig. 3 (a-c) shows new vesicles developing in previously normal skin at the margins of an excision scar and Fig. 4 (a, b) in a full thickness graft. Conclusioti
The conclusion reached from this basic set of observations is that in L.C. there is something wrong with the lymphatic system ofthe site and not just with the dilated vessels in the skin, nor indeed with the skin itself. It seems that the primary fault must lie somewhere at a deeper plane, beneath the skin, and that one ofthe effects of this deep abnormality is to cause saccular dilatation of superficial lymphatics in a circumscribed area of overlying skin. Observations (6) Similar vesicles formed by saccular dilatations of superficial lymphatics sometimes occur in association with lymphoedema of a hmb or scrotum due to acquired lymphatic obstruction. This suggests that such vesicles are the result of raised intralymphatic pressure (Fig. 5). (7) In the conventional excision specimen of L.C, consisting of full thickness dermis and a partial layer of subcutaneous fat, there are always abnormally large lymphatics, some with muscle coats, to be seen transected at the lower margin of the specimen. These can be traced in serial sections to communicate with the more superficial thin-walled dermal vessels and via them with the vesicles (Figs 6 and 7).
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V,
FIGURE 5. MaSe aged 53 years. Subepidermal lymphatic vesicle from the scrotum of a patient with severe lymphoedema due to acquired lymphatic obstruction. The appearance of the vesicle is indistinguishable from one of L.C. FIGURE 6. Inadequate depth of excision. Section through the lower margin of an 'orthodox' excision specimen of L.C. The plane of excision (arrowed) was 15-20 mm below the skin surface and, as can be seen, grossly dilated muscle-coated lymphatics (L) in the subcutis have been transected at operation and their deeper parts left in the patient. As in the case shown in Fig. 3 new vesicles were developing around the scar a year later. Conclusion The conclusion drawn from these two observations is that the large vessels in L . C , running mainly vertically through the dermis, are transmitting raised pressure to the superficial vesicles. Furthermore it seems that this raised pressure must come from some peculiarly localized and confined source rather than from the lymphatic system proper; otherwise there would be lymphoedema, at least of the
Epidermis
Dermis
----(]--0---Tronsected vessels(as in Fig.6) Subcufis
Deep fascio
FIGURE 7. Diagram to illustrate the histological findings in L.C. specimens excised with only part of the thickness of subcutaneous fat. Included in such specimens are the subepidermal vesicles and the superficial dilated vessels from which they arise, together with large dilated vessels in the dermis and subcutis. But at the deep margin of the excision these vessels are cut across and their proximal parts remain in the bed of the wound.
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area of skin containing the vesicles, if not of the whole of the limb or of the region of the trunk concerned. And L.C. is in my experience never accompanied by oedema. Observation
(8) It is not unusual to find histioqrtes (macrophages) and even giant cells lying free within the lumen of the dilated dermal lymphatics in L.C. These cells may occur singly or in quite large clumps. Frequently their cytoplasm is vacuolated and on occasions they can be seen to have ingested red blood cells or to contain iron pigment (Fig. 8a-c).
FIGURE 8. (a) Dilated L.C. vessele containing large foamy histiocytes and some red cells. (b) Dilated L.C vessel containing histiocytes laden with iron pigment. (c) Vesicle from a superficially inflamed area of L,C. The lumen contains a giant coll as well as lymphocytes and histiocytes. Conclusion
The presence of such phagocytic cells lying free within the lumen of a vessel strongly suggests that there is not a normal fiow of fluid within the vessel concerned. It suggests that there is no true circulation in or drainage from these vessels and that they may form part of a closed system in which the fiuid is almost static. Observation
(9) As stated earlier it is common for L.C. vesicles to have their clear, colourless fiuid contaminated by varying quantities of red cells. This mixture of blood and lymphangioma fiuid occurs predominantly at the most peripheral part of the lesion, in the vesicles and the thin-walled dilated lymphatics just beneath them. It seems that minor hacmangiolymphatic connections must occur now and again, perhaps caused by mild trauma, in the region where blood capillaries are lying immediately adjacent to dilated lymphatics and indeed often stretched by them (Fig. 9a, b). Vesicles which have become pink or red due to blood contamination remain so for weeks before clearing. And vesicles which have become filled with pure blood turn black, dry up and fall off. Histologically such vesicles are seen to be entirely filled by packed red cells (Fig. 9c, d). Conclusion
These observations concerning the contamination of vesicle fluid by blood further support the sug-
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FIGURE 9. (a) L.C. vesicles with a small number of red cells in their fluid. These vesicles were macroscopically pink. (b) L . C vesicle containing about 50" „ of red cells in its fluid. There are also a few histiocytes present. This vesicle was macroscopically red. (c, d) L.C vesicle whose lumen is filled with packed red cells. This vesicle, which was macroscopically blackish red, would shortly have dried up and fallen off as a little black crust. The epidermis overlying it is already becoming necrotic.
gestion that there is no true circulation in or drainage from the vesicles. If there were, red cells entering vesicles would be rapidly flushed away and not remain until phagocytoscd by histiocytes or congealed into a solid mass. Observation
(10) As a result of these preliminary observations, and the conclusions which they suggested, it was decided to encourage the surgeons to excise L.C. lesions more deeply; in fact right down to the level of the deep fascia. When such deep excision specimens came to hand and were dissected it was found that the large dermal lymphatics could be followed down through the subcutaneous fat and into one or more large cisterns lying just above the deep fascia. These very large spaces, often several centimetres in diameter, do not have the form of linear vessels but are cystic, often with trabeculated linings and always with abundant smooth muscle in their walls. Individual cisterns are commonly multilocular and beneath most areas of L.C. there is more than one cistern present (Fig. ioa-c). When multiple the cisterns do not interconnect. Numerous lymphatic vessels lead out of these cisterns
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Dermis
(a
(c)
FIGURE IO. (a) A slice through a deep exision specimen of L.C. The depth of the subcutaneous tissue excised was 40 mm and in its deepest part is a typical cistern, multilocular and with a trabeculated wall. (The arrows indicate the plane of 'conventional' excision.) (b) Deep excision specimen from another case. The depth of tissue removed was 55 mm. Several separate cisterns were present, three of them shown in this photograph. B is still filled by lymphangioma fluid, clotted by fixation, while A and C have had their contents removed. Note the strongly trabeculated wall of C. (The arrows indicate the plane of 'conventional' excision.) (c) Subcutaneous tissue 50 mm in depth removed from beneath the L.C. shown in Fig. i. Several cisterns were present and parts of two of them, each about 30 mm diameter, are shown. Note the very thick (2 mm) trabeculated wall of A. The histology of this cistern is shown in Fig, iia,
and run up through the subcutaneous fat to communicate with the large dermal lymphatics, and thence to the surface of the skin. There is no sign of any vessels leaving the deep aspect of these cisterns to join the main lymphatics which he at that plane and drain centrally (Fig, iia, b). Conclusion
These findings seemed to support the growing belief that the abnormal vessels of L.C. may form part of a closed system. The presence of a well-developed muscle coat around tbe cisterns suggested that this muscle must do something; either exercise a continous tone or else contract intermittently and pulsate like the peripheral lymph hearts of lower vertebrates, or both.
HYPOTHESIS
The hypothesis arrived at by the dissection and histotogical examination of a series of full depth excision specimens of L.C. was thus as follows. The complete lesion consists of an apparently closed system of lymphatic vessels, arising from large muscle-coated cisterns which lie just above the deep fascia and exert a continuous or intermittent pressure on their contained fluid, which is transmitted
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FIGURE II. (a) Low power view of part of the large cistern A shown in Fig. ioc. It was 30 mm in diameter and its muscular wall 2 mm thick. (b) Higher magnification of part of the muscular wall of a cistern from a different case, showing one of the vessels which traverse the wall and expand outside it into leashes of dilated lymphatics.
through the skin via large dilated lymphatics to the surface, where saccular dilatation of subepidermal lymphatics occurs, giving rise to the clinically visible vesicles (Fig. 12). Observations made in vivo (11) Lymphangiography has been carried out in the majority of cases in this series. In all the cases so studied normal lymphangiograms of the related limb have been obtained and in no case has there been any filling of the cisterns or other parts of the lymphangioma. There is, it seems, no retrograde connection between the normal main lymphatics and the cisterns. Epidermis Dermis
Subcufis
Deep fosC'Q
FIGURE 12, Diagram to illustrate the hypothetical reconstruction of a complete L.C. lesion. In fact the abnormal lymphatics running from the cisterns to the skin surface are much more complex in their layout than portrayed here. They adopt a meandering course with frequent anastomoses and branchings and many have varicosities along their course.
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ill) On a number of occasions dye or contrast medium has been injected into the cisterns at operation and has been observed not to drain away into any normal lymphatics. The cisterns appear to be truly isolated from the main lymphatics of the region. (13) It has been confirmed that when multiple the cisterns do not intercommunicate. If one is punctured during operation and its contained fluid leaks out, the others do not become deflated. And dye injected into one cistern does not appear in neighbouring ones. (14) When the lesion is being undercut at the plane of the deep fascia it has been observed that the cisterns do not leak or collapse, and by the time such specimens arrive in the laboratory they are still full of fluid (Fig. iob). (15) At no time has the operating surgeon in the course of undercutting the cisterns been able to detect any connections at all between them and the normal lymphatics of the region.
Pressure in cysf {mm Hg; 10 20 Pressure in subcutoneous 1 0 fissue (mm Hg)
I-S.T
I
I
1 mm
A
Flush
A
FiJsh
FIGURE 13. The upper tracing is from a cannula inserted into an L.C. cistern. It shows fairly regular pulsations, initially at the rate of about 4 per min. The minor fluctuations shown on this tracing are those of the respiratory rhythm. On two occasions the cannula became blocked and was cleared by flushing, after which the pulsations began again. The lower tracing is from a control cannula inserted into subcutaneous fat adjacent to the cistern. It records only cardiac and respiratory rhythms. It will be seen that the minimal pressure maintained within the cistern between pulsations is slightly above that of the pressure recorded by the control cannula. This suggests that the cistern maintains a small but constant tone as well as contracting intermittently.
Conclusion
While these operative findings all seem to confirm the hypothesis that the lymphangioma is a closed system, by doing so they raise a further problem. If, as it appears, the abnormal vessels and cisterns of the lymphangioma are a closed system, not connected to the general lymphatics and not receiving a retrograde supply of lymph from them, whence comes the pressure within the lymphangiomatous vessels, responsible for their dilatation ? The most likely source seemed to be the muscle coats of the cisterns. Observation
(16) In two cases of typical L.C. a cannula was inserted into one of the cisterns at operation. Tracings were made of the pressure within the cisterns and this was shown to rise and fall with a steady but very slow pulse rate of about 4 to 8 beats per minute, entirely independent of that of the cardiovascular system and of respiration. This rate of pulsation is of the same order as that which has been observed (Kinmonth, 1972) in normal large lymphatics such as the thoracic duct (Figs 13 and 14).
Pathology of lymphangioma circumscriptum
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20r
Pressure in cyst (mm Hg] 20
V. N. N
^-**-«w'wwJ >— ,Ul
Pressure in 5ubcutaneoos iissue (mm Hg)
S.T,
FIGURE 14. Similar tracing to show the response of a cistern to percussion. At the point P i the tissue adjacent to the cistern wall was gently tapped. The direct effect of this is shown on the tracing by a steep and instantaneous rise and fall in pressure, to which the cistern responded a few seconds later by a spontaneous contraction. At points P 2-5 a series of gentle taps was given, each progressively closer to the cistern wall. These are recorded as a series of increasingly steep instantaneous pressure rises. The response of the cistern to this stimulation was a burst of contractions at a higher than normal rate, and there was also a rise in the level of the minimal pressure maintained in the cistern, i.e. an increase in tone. Conclusion
All these observations made in vivo support the morbid anatomical hypothesis that the abnormal vessels of L.C. stem from one or more underlying cisterns, and extend it by showing that their mnscle coats pulsate slowly, causing fluctuation of the pressure within them. It seems likely that this pressure is transmitted from the cisterns, up through the abnormal subcutaneous and dermal lymphatics to reach the surface where the vesicles occur. NATURAL HISTORY
The commonest history given in cases of L.C. is that a few vesicles were noticed in the skin at or shortly after birth, and that these have increased in number and in the area of skin they occupy during subsequent years. Other cases have a history that at birth there were neither vesicles nor any other abnormality detected and that the first sign of the lesion was the development of vesicles several years after birth. There is, however, a third group of cases which is perhaps the most enlightening. In these, of which ten have been encountered in the present series, the child at birth was observed to have a deep subcutaneous cystic swelling, usually situated either in relationship to the axilla or the base of the neck, or in the vicinity of the groin or buttock. At birth this swelling was the only abnormality detectable and there were no vesicles present in the overlying skin (Fig. 15a). These deep congenital cysts have on occasions been drained by aspiration or incision and in these cases they have fairly rapidly refilled. In more than one instance the axilla was explored surgically shortly after birth and the largest of the cysts removed intact, but it was noted at operation that others were present deeper in the axilla and these were left in situ. The cysts which were excised showed histologically that they had the typical appearances of lymphangiomatous cisterns, with a thick muscular wall (Fig. 15b). These deep cystic swellings which are present at birth seem to correspond to the condition generally known as cystic hygroma. The point of interest about these cases is that when followed for a
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FIGURE 15. (a) Neonatal infant with congenital cysts deep in the subcutaneous tissue of the left upper chest wall. This region was explored surgically shortly after birth and the largest cyst removed. But others, smaller and deeper in the axilla, were left in situ. (b) Section through the wall of the cyst removed from the infant shown in (a). In the collapsed and fixed state its wal! was from i to 2 mm thick and its diameter 20 mm. The wall is formed of fibrous tissue liberally interlaced with smooth muscle. Small vessels can be seen traversing the wall, issuing outside it as dilated thin-walled lymphatics. The structure of this cystic hygroma is indistinguishable from that of an L.C, cistern. (c) The same child as in (a) but 8 years later. Typical L.C. vesicles have developed near the scar. (d) Histology of vesicles from the child as shown in (c). They have developed in skin which at birth appeared normal.
few years typical L.C. vesicles have developed in the skin overlying the congenital cysts, or the site from which the cysts had been partially excised (Fig. 15c, d). From these observations ofthe natural history it seems possible that in all cases the deep cisterns ofthe lesion are present at birth and that in some cases they have already given rise to overlying vesicles by that time. But in other cases, while the cisterns are detected at birth as deep swellings, the vesicles do not become apparent for a year or more afterwards. It may well be supposed therefore that there are other cases, perhaps the majority, in which subcutaneous cisterns are present at birth but not large enough or in such a position as to call attention to themselves. In such cases the first indication ofthe abnormality would be the development of vesicles later.
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PATHOGENESIS
As has been stated above there are certain cases in which the natural history strongly suggests that the primary and congenital component of the L.C. lesion is the deep one. It can therefore be put forward as a hypothesis that the child is born with one or more isolated cisterns in the deep subcutaneous plane, and with an otherwise normal lymphatic system. It is a matter for conjecture as to how the cisterns might arise, but perhaps the most likely possibility is that they represent embryonic lymph sacs which have failed to link up with their fellows. These sacs develop initially in the embryo as separate structures and become interconnected later to form a continuous system of vessels. As has been pointed out before (Peachey et al., 1970) the majority of L.C. lesions are situated in relationship to the base of a hmb and/or that part of the trunk to which it is connected. That is to say they occupy the regions from which limb buds developed in the embryo. It is thought possible that the sequestration of one or more lymph sacs in the embryo may occur at an early stage of limb development, and that once this has occurred the foundation of a future lymphangioma has been laid. Pursuing this hypothesis it could be supposed that a wholly new and abnormal set of superfluous vascular channels, with dilated lumina and hypertrophied walls, grow out from the congenital cistern towards the skin, as a kind of 'blow-out' phenomenon secondary to the pressure created by the pulsation and tone of the muscle coat of the cistern. Such vessels would have no real circulation in them, only at best an ebb and flow, and they could not function as a drainage system for the skin. Therefore to make this hypothesis compatible with the absence of oedema in lymphangiomatous skin it would have to be supposed that in addition to the abnormal, dilated, functionless vessels arising from the cisterns the skin also contains a system of normal lymphatics with proper central connections responsible for its drainage. Observation
(17) Dye was injected intradermally into macroscopically normal skin within an area of L.C. When the subcutaneous tissues were subsequently explored in the quest for cisterns it was observed by the surgeon that there was a normal number of normal sized lymphatics draining dye from the injection site. These ran down through the subcutaneous fat alongside the dilated abnormal lymphatics ofthe L.C. There was no connection between the normal and the abnormal vessels and neither the abnormal vessels nor the cisterns contained dye. Conclusion
Within an area of L.C. there are two intermingled but separate sets of lymphatics, one normal in structure and in its function of draining the skin; the other dilated, hypertrophic and seeming to perform no useful function as a drainage system. THERAPEUTIC IMPLICATIONS
If it is accepted that the primary fault underlying L.C. is the congenital presence of isolated muscular cisterns, and that the abnormal vessels leading from them towards the skin surface are blind outgrowths from the cisterns, formed in response to their tone and pulsation pressure, then this will have two immediate implications concerning therapy. (i) It must be regarded as futile to remove the skin containing the vesicles and a partial thickness of subcutaneous fat containing abnormal and dilated vessels (i.e. the tissue above the arrows in Fig. roa, b) if the cisterns 'feeding' them are left in situ. Following such incomplete excision the original cisterns will simply sprout new abnormal vessels and subsequently give rise to new vesicles, as in Figs 3 and 4.
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(2) If the cisterns are indeed the primary cause of all the more superficial abnormalities it may well prove to be adequate to remove just the cisterns (i.e. the tissue below the arrows in Fig. loa, b) and leave the skin and upper subcutaneous layer intact. If the cisterns arc the driving force behind the development of the other parts of the lesion (as the natural history of certain cases suggests) their removal might allow these other parts to involute. The cosmetic results of this type of selective deep excision, with skin preservation, would clearly be better than those of total radical excision. Excision of all the affected skin and subcutaneous tissue down to the deep fascia would in many cases (e.g. Fig. i) be a mutilating procedure. The high recurrence rate after surgery in the past may to a large extent be attributed to surgeons erring on the conservative side, but misguidedly tending to conserve the most important part of the lesion, the deep part. In nine cases to date surgery has been aimed at removing as many as possible of the cisterns and preserving as much as possible of the overlying skin. Quite small ellipses of skin containing half or much less of all the vesicles present have been excised, the margins of the wounds undercut in all directions and the underlying cisterns located and removed down to the level of the deep fascia. The wounds have then been closed, leaving vesicles still present in the adjacent skin. The results have so far been the exact opposite to those shown in Figs 3 and 4. No new vesicles have formed and those that remained in the skin after operation have disappeared. An account of the longer follow-up of patients treated by this method will be made the subject of a future publication. ACKNOWLEDGMENTS
The author wishes to express his gratitude to the various dermatological and surgical colleagues who in one way or another have steered excision specimens of L.C. into his hands; especially to Professors N.L.Browse and J.B.Kinmonth, without whose assistance this study could not have progressed beyond the armchair stage. Particular thanks are due to Professor Browse for carrying out, at the author's request, the procedures on which observations 16 and 17 were dependent. Theauthor also wishes to thank Mr David Lane A.I.M.L.T. for technical assistance with the histology. Miss June Thorogood A.I.A.T. for photographic assistance and Mrs Ann Cater for secretarial assistance. This work was partly supported by a grant from the Wellcome Trust, for which the author is deeply grateful. REFERENCES KiNMONTH, J.B. (1-972) The lymphatics. Edward Arnold, London. PEACHEY, R.D.G., LIM, C-C. & WHIMSTEB, L W . (1970) Lymphangioma of skin. A review of 65 cases. British Jourjial of Dermatology, 83, 519.
Clinical and Laboratory Investigations
The pathology of lymphangioma circumscriptum I.W.WHIMSTER Department of Dermatology, St Thomas' Hospital and Medical School, London SEi
Accepted for publication 30 August 1975
SUMMARY
A Study of lymphangioma circumscriptum has been carried out over a number of years in an attempt to understand its nature and pathogenesis, with a view to improving treatment. It is postulated that the lesion consists essentially of a collection of large muscular-coated lymphatic cisterns, lying deep in the subcutaneous plane and communicating via dilated dermal lymphatics with the superficial vesicles. It seems that these cisterns do not communicate directly, if at all, with the general lymphatic system but represent a sequestrated part of it. They have been shown by cannulation to pulsate at a slow steady rate producing a rise and fall of pressure within them. It is believed that the vesicles are saccular dilatations of superficial lymphatics, secondary to raised pressure transmitted from the pulsating cisterns beneath. It is suggested that it may be possible to treat these lesions more successfully and with better cosmetic results by excising the subcutaneous cisterns and leaving the overlying skin intact.
Lymphangioma circumscriptum (L.C.) is characterized clinically by the presence within a circumscribed area of skin of vesicles, mostly filled with clear colourless fluid but occasionally tinged with varying quantities of blood, the colour then ranging from pink, through red to black. The clinical aspects of the condition were reviewed by Peachey, Lim & Whimstcr in 1970. The present article is concerned entirely with the type of lesion defined by these authors as the 'classical' form (Fig. i).
FIGURE I. A circumscribed group of L.C. vesicles, ranging from colourless to dark red, just above the left iliac crest of a girl of 14 years. They had been present and increasing in numbers since the age of 6 years. Beneath the involved skin there was a deep diffuse subcutaneous swelling. * Extension of a paper presented at the B.A.D. Meeting, London, July 1974. 473
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The condition is usually present at birth or develops soon afterwards, commonly becoming more intense throughout childhood and persisting indefinitely. It is a nuisance to the patient, not only because of the cosmetic disfigurement caused by the presence of the vesicles but also because of their tendency to rupture and leak fluid which stains clothing. While being well known and easily recognized by its clinical manifestations there were two features about the condition which seemed to call for further investigation. First, its pathogenesis was unknown and, secondly, it was apparent that present methods of treatment were profoundly unsatis-
FIGURE 2 (a) Skin from within an area of L.C. but between vesicles. In the upper dermis there are grossly dilated lymphatic vessels orientated mainly in the horizontal plane. (b) Enlarged and dilated muscle-coated lymphatic running vertically in the lower dermis beneath an area of vesicles. (c) An early stage in vesicle formation. The dilated vessels in the photograph can be seen in serial sections to be interconnected. Beneath the epidermis is a very dilated thin walled lymphatic arising from the horizontal vessels as a blind-ended sac. (d) Fully formed L.C. vesicle occupying a whole papilla and arising like a balloon from a horizontal vessel lying just below the papillary layer.
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factory. It was felt that if the pathology of the condition were better understood this might in turn lead to improved methods of therapy. This article is an attempt to set out the progressive series of observations which have been made over a number of years of the morbid anatomy, the histology and the natural history of the condition, together with the sequence of conclusions, hypotheses and further investigations arising out of them. The study has been based mainly on thirty cases from which whole surgical excision specimens were available for dissection and histological examination by the author, backed up by many further cases from which less complete material was available. Observations (1) However large or small the area of skin involved in L.C. may be, it is as the name implies a circumscribed one. The arrangement of herpes zoster lesions within a characteristically circumscribed area of skin, as opposed to the diffuse scattering of varicella lesions, led to the recognition of the reason for this grouping and to the common link between all the lesions of a group; a posterior root ganglion. It was felt that the circumscribed grouping of L.C. vesicles must have a similar significance, in that it indicated the presence of some underlying link between ail the individual and apparently separate vesicles within the circumscribed area. (2) In L.C. the dermis immediately beneath the papillary layer contains dilated thin-walled lymphatics mainly orientated horizontally, and deep to these are others, some with thicker walls, mainly running vertically (Fig. 2a, b). (3) The vesicles of L.C. are saccular dilatations bulging out from thin-walled lymphatics and projecting upwards to occupy the papillae only when sufficiently distended. So far as I have personally been able to convince myself there are no lymphatics in normal dermal papillae (Fig. 2c, d). (4) The vesicles are often not present at birth, and even when some are, others certainly arise later. This suggests that the dilatation of the saccular vessels is not due to any intrinsic fault of the normal
FIGURE 3. (a) A girl aged 9 years with a group of L.C. vesicles on the right shoulder. Two vesicles were present at birth and their number had increased subsequently. (b) The same patient 6 months after excision of almost all the affected skin together with subcutaneous tissue to a total depth of 10 mm. There wore large abnormal lymphatics transected at the base of the excision specimen. At this post-operative stage there are already a few new vesicles forming alongside the scar. (c) The same patient 2 years later. There are now almost as many newly formed vesicles in the area as there were in the original lesion.
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FIGURE 4. (a) Female aged 18 years. A vesicle from an area of typical L.C. The affected skin was excised and the wound repaired with a full thickness pedicle graft. Subsequently the graft developed abundant new vesicles. (b) The same patient as in (a). A vesicle in the graft about 18 months after operation.
dermal lymphatics of the area concerned but that the fault, whatever its nature, is an acquired one, affecting vessels which either appeared normal previously or were not in existence at that time. (5) After excision of lymphangiomatous skin, with the full thickness of dermis and including all the vesicles present, 'recurrence' of vesicles (that is to say the formation of new vesicles) is the rule, whether the wound has been sutured or grafted. This phenomenon indicates that skin whose superficial lymphatics have previously behaved normally can be made to develop saccular ones as a result of its coming to occupy the site of the original lesion. Fig. 3 (a-c) shows new vesicles developing in previously normal skin at the margins of an excision scar and Fig. 4 (a, b) in a full thickness graft. Conclusioti
The conclusion reached from this basic set of observations is that in L.C. there is something wrong with the lymphatic system ofthe site and not just with the dilated vessels in the skin, nor indeed with the skin itself. It seems that the primary fault must lie somewhere at a deeper plane, beneath the skin, and that one ofthe effects of this deep abnormality is to cause saccular dilatation of superficial lymphatics in a circumscribed area of overlying skin. Observations (6) Similar vesicles formed by saccular dilatations of superficial lymphatics sometimes occur in association with lymphoedema of a hmb or scrotum due to acquired lymphatic obstruction. This suggests that such vesicles are the result of raised intralymphatic pressure (Fig. 5). (7) In the conventional excision specimen of L.C, consisting of full thickness dermis and a partial layer of subcutaneous fat, there are always abnormally large lymphatics, some with muscle coats, to be seen transected at the lower margin of the specimen. These can be traced in serial sections to communicate with the more superficial thin-walled dermal vessels and via them with the vesicles (Figs 6 and 7).
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V,
FIGURE 5. MaSe aged 53 years. Subepidermal lymphatic vesicle from the scrotum of a patient with severe lymphoedema due to acquired lymphatic obstruction. The appearance of the vesicle is indistinguishable from one of L.C. FIGURE 6. Inadequate depth of excision. Section through the lower margin of an 'orthodox' excision specimen of L.C. The plane of excision (arrowed) was 15-20 mm below the skin surface and, as can be seen, grossly dilated muscle-coated lymphatics (L) in the subcutis have been transected at operation and their deeper parts left in the patient. As in the case shown in Fig. 3 new vesicles were developing around the scar a year later. Conclusion The conclusion drawn from these two observations is that the large vessels in L . C , running mainly vertically through the dermis, are transmitting raised pressure to the superficial vesicles. Furthermore it seems that this raised pressure must come from some peculiarly localized and confined source rather than from the lymphatic system proper; otherwise there would be lymphoedema, at least of the
Epidermis
Dermis
----(]--0---Tronsected vessels(as in Fig.6) Subcufis
Deep fascio
FIGURE 7. Diagram to illustrate the histological findings in L.C. specimens excised with only part of the thickness of subcutaneous fat. Included in such specimens are the subepidermal vesicles and the superficial dilated vessels from which they arise, together with large dilated vessels in the dermis and subcutis. But at the deep margin of the excision these vessels are cut across and their proximal parts remain in the bed of the wound.
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area of skin containing the vesicles, if not of the whole of the limb or of the region of the trunk concerned. And L.C. is in my experience never accompanied by oedema. Observation
(8) It is not unusual to find histioqrtes (macrophages) and even giant cells lying free within the lumen of the dilated dermal lymphatics in L.C. These cells may occur singly or in quite large clumps. Frequently their cytoplasm is vacuolated and on occasions they can be seen to have ingested red blood cells or to contain iron pigment (Fig. 8a-c).
FIGURE 8. (a) Dilated L.C. vessele containing large foamy histiocytes and some red cells. (b) Dilated L.C vessel containing histiocytes laden with iron pigment. (c) Vesicle from a superficially inflamed area of L,C. The lumen contains a giant coll as well as lymphocytes and histiocytes. Conclusion
The presence of such phagocytic cells lying free within the lumen of a vessel strongly suggests that there is not a normal fiow of fluid within the vessel concerned. It suggests that there is no true circulation in or drainage from these vessels and that they may form part of a closed system in which the fiuid is almost static. Observation
(9) As stated earlier it is common for L.C. vesicles to have their clear, colourless fiuid contaminated by varying quantities of red cells. This mixture of blood and lymphangioma fiuid occurs predominantly at the most peripheral part of the lesion, in the vesicles and the thin-walled dilated lymphatics just beneath them. It seems that minor hacmangiolymphatic connections must occur now and again, perhaps caused by mild trauma, in the region where blood capillaries are lying immediately adjacent to dilated lymphatics and indeed often stretched by them (Fig. 9a, b). Vesicles which have become pink or red due to blood contamination remain so for weeks before clearing. And vesicles which have become filled with pure blood turn black, dry up and fall off. Histologically such vesicles are seen to be entirely filled by packed red cells (Fig. 9c, d). Conclusion
These observations concerning the contamination of vesicle fluid by blood further support the sug-
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FIGURE 9. (a) L.C. vesicles with a small number of red cells in their fluid. These vesicles were macroscopically pink. (b) L . C vesicle containing about 50" „ of red cells in its fluid. There are also a few histiocytes present. This vesicle was macroscopically red. (c, d) L.C vesicle whose lumen is filled with packed red cells. This vesicle, which was macroscopically blackish red, would shortly have dried up and fallen off as a little black crust. The epidermis overlying it is already becoming necrotic.
gestion that there is no true circulation in or drainage from the vesicles. If there were, red cells entering vesicles would be rapidly flushed away and not remain until phagocytoscd by histiocytes or congealed into a solid mass. Observation
(10) As a result of these preliminary observations, and the conclusions which they suggested, it was decided to encourage the surgeons to excise L.C. lesions more deeply; in fact right down to the level of the deep fascia. When such deep excision specimens came to hand and were dissected it was found that the large dermal lymphatics could be followed down through the subcutaneous fat and into one or more large cisterns lying just above the deep fascia. These very large spaces, often several centimetres in diameter, do not have the form of linear vessels but are cystic, often with trabeculated linings and always with abundant smooth muscle in their walls. Individual cisterns are commonly multilocular and beneath most areas of L.C. there is more than one cistern present (Fig. ioa-c). When multiple the cisterns do not interconnect. Numerous lymphatic vessels lead out of these cisterns
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Dermis
(a
(c)
FIGURE IO. (a) A slice through a deep exision specimen of L.C. The depth of the subcutaneous tissue excised was 40 mm and in its deepest part is a typical cistern, multilocular and with a trabeculated wall. (The arrows indicate the plane of 'conventional' excision.) (b) Deep excision specimen from another case. The depth of tissue removed was 55 mm. Several separate cisterns were present, three of them shown in this photograph. B is still filled by lymphangioma fluid, clotted by fixation, while A and C have had their contents removed. Note the strongly trabeculated wall of C. (The arrows indicate the plane of 'conventional' excision.) (c) Subcutaneous tissue 50 mm in depth removed from beneath the L.C. shown in Fig. i. Several cisterns were present and parts of two of them, each about 30 mm diameter, are shown. Note the very thick (2 mm) trabeculated wall of A. The histology of this cistern is shown in Fig, iia,
and run up through the subcutaneous fat to communicate with the large dermal lymphatics, and thence to the surface of the skin. There is no sign of any vessels leaving the deep aspect of these cisterns to join the main lymphatics which he at that plane and drain centrally (Fig, iia, b). Conclusion
These findings seemed to support the growing belief that the abnormal vessels of L.C. may form part of a closed system. The presence of a well-developed muscle coat around tbe cisterns suggested that this muscle must do something; either exercise a continous tone or else contract intermittently and pulsate like the peripheral lymph hearts of lower vertebrates, or both.
HYPOTHESIS
The hypothesis arrived at by the dissection and histotogical examination of a series of full depth excision specimens of L.C. was thus as follows. The complete lesion consists of an apparently closed system of lymphatic vessels, arising from large muscle-coated cisterns which lie just above the deep fascia and exert a continuous or intermittent pressure on their contained fluid, which is transmitted
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FIGURE II. (a) Low power view of part of the large cistern A shown in Fig. ioc. It was 30 mm in diameter and its muscular wall 2 mm thick. (b) Higher magnification of part of the muscular wall of a cistern from a different case, showing one of the vessels which traverse the wall and expand outside it into leashes of dilated lymphatics.
through the skin via large dilated lymphatics to the surface, where saccular dilatation of subepidermal lymphatics occurs, giving rise to the clinically visible vesicles (Fig. 12). Observations made in vivo (11) Lymphangiography has been carried out in the majority of cases in this series. In all the cases so studied normal lymphangiograms of the related limb have been obtained and in no case has there been any filling of the cisterns or other parts of the lymphangioma. There is, it seems, no retrograde connection between the normal main lymphatics and the cisterns. Epidermis Dermis
Subcufis
Deep fosC'Q
FIGURE 12, Diagram to illustrate the hypothetical reconstruction of a complete L.C. lesion. In fact the abnormal lymphatics running from the cisterns to the skin surface are much more complex in their layout than portrayed here. They adopt a meandering course with frequent anastomoses and branchings and many have varicosities along their course.
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ill) On a number of occasions dye or contrast medium has been injected into the cisterns at operation and has been observed not to drain away into any normal lymphatics. The cisterns appear to be truly isolated from the main lymphatics of the region. (13) It has been confirmed that when multiple the cisterns do not intercommunicate. If one is punctured during operation and its contained fluid leaks out, the others do not become deflated. And dye injected into one cistern does not appear in neighbouring ones. (14) When the lesion is being undercut at the plane of the deep fascia it has been observed that the cisterns do not leak or collapse, and by the time such specimens arrive in the laboratory they are still full of fluid (Fig. iob). (15) At no time has the operating surgeon in the course of undercutting the cisterns been able to detect any connections at all between them and the normal lymphatics of the region.
Pressure in cysf {mm Hg; 10 20 Pressure in subcutoneous 1 0 fissue (mm Hg)
I-S.T
I
I
1 mm
A
Flush
A
FiJsh
FIGURE 13. The upper tracing is from a cannula inserted into an L.C. cistern. It shows fairly regular pulsations, initially at the rate of about 4 per min. The minor fluctuations shown on this tracing are those of the respiratory rhythm. On two occasions the cannula became blocked and was cleared by flushing, after which the pulsations began again. The lower tracing is from a control cannula inserted into subcutaneous fat adjacent to the cistern. It records only cardiac and respiratory rhythms. It will be seen that the minimal pressure maintained within the cistern between pulsations is slightly above that of the pressure recorded by the control cannula. This suggests that the cistern maintains a small but constant tone as well as contracting intermittently.
Conclusion
While these operative findings all seem to confirm the hypothesis that the lymphangioma is a closed system, by doing so they raise a further problem. If, as it appears, the abnormal vessels and cisterns of the lymphangioma are a closed system, not connected to the general lymphatics and not receiving a retrograde supply of lymph from them, whence comes the pressure within the lymphangiomatous vessels, responsible for their dilatation ? The most likely source seemed to be the muscle coats of the cisterns. Observation
(16) In two cases of typical L.C. a cannula was inserted into one of the cisterns at operation. Tracings were made of the pressure within the cisterns and this was shown to rise and fall with a steady but very slow pulse rate of about 4 to 8 beats per minute, entirely independent of that of the cardiovascular system and of respiration. This rate of pulsation is of the same order as that which has been observed (Kinmonth, 1972) in normal large lymphatics such as the thoracic duct (Figs 13 and 14).
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20r
Pressure in cyst (mm Hg] 20
V. N. N
^-**-«w'wwJ >— ,Ul
Pressure in 5ubcutaneoos iissue (mm Hg)
S.T,
FIGURE 14. Similar tracing to show the response of a cistern to percussion. At the point P i the tissue adjacent to the cistern wall was gently tapped. The direct effect of this is shown on the tracing by a steep and instantaneous rise and fall in pressure, to which the cistern responded a few seconds later by a spontaneous contraction. At points P 2-5 a series of gentle taps was given, each progressively closer to the cistern wall. These are recorded as a series of increasingly steep instantaneous pressure rises. The response of the cistern to this stimulation was a burst of contractions at a higher than normal rate, and there was also a rise in the level of the minimal pressure maintained in the cistern, i.e. an increase in tone. Conclusion
All these observations made in vivo support the morbid anatomical hypothesis that the abnormal vessels of L.C. stem from one or more underlying cisterns, and extend it by showing that their mnscle coats pulsate slowly, causing fluctuation of the pressure within them. It seems likely that this pressure is transmitted from the cisterns, up through the abnormal subcutaneous and dermal lymphatics to reach the surface where the vesicles occur. NATURAL HISTORY
The commonest history given in cases of L.C. is that a few vesicles were noticed in the skin at or shortly after birth, and that these have increased in number and in the area of skin they occupy during subsequent years. Other cases have a history that at birth there were neither vesicles nor any other abnormality detected and that the first sign of the lesion was the development of vesicles several years after birth. There is, however, a third group of cases which is perhaps the most enlightening. In these, of which ten have been encountered in the present series, the child at birth was observed to have a deep subcutaneous cystic swelling, usually situated either in relationship to the axilla or the base of the neck, or in the vicinity of the groin or buttock. At birth this swelling was the only abnormality detectable and there were no vesicles present in the overlying skin (Fig. 15a). These deep congenital cysts have on occasions been drained by aspiration or incision and in these cases they have fairly rapidly refilled. In more than one instance the axilla was explored surgically shortly after birth and the largest of the cysts removed intact, but it was noted at operation that others were present deeper in the axilla and these were left in situ. The cysts which were excised showed histologically that they had the typical appearances of lymphangiomatous cisterns, with a thick muscular wall (Fig. 15b). These deep cystic swellings which are present at birth seem to correspond to the condition generally known as cystic hygroma. The point of interest about these cases is that when followed for a
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FIGURE 15. (a) Neonatal infant with congenital cysts deep in the subcutaneous tissue of the left upper chest wall. This region was explored surgically shortly after birth and the largest cyst removed. But others, smaller and deeper in the axilla, were left in situ. (b) Section through the wall of the cyst removed from the infant shown in (a). In the collapsed and fixed state its wal! was from i to 2 mm thick and its diameter 20 mm. The wall is formed of fibrous tissue liberally interlaced with smooth muscle. Small vessels can be seen traversing the wall, issuing outside it as dilated thin-walled lymphatics. The structure of this cystic hygroma is indistinguishable from that of an L.C, cistern. (c) The same child as in (a) but 8 years later. Typical L.C. vesicles have developed near the scar. (d) Histology of vesicles from the child as shown in (c). They have developed in skin which at birth appeared normal.
few years typical L.C. vesicles have developed in the skin overlying the congenital cysts, or the site from which the cysts had been partially excised (Fig. 15c, d). From these observations ofthe natural history it seems possible that in all cases the deep cisterns ofthe lesion are present at birth and that in some cases they have already given rise to overlying vesicles by that time. But in other cases, while the cisterns are detected at birth as deep swellings, the vesicles do not become apparent for a year or more afterwards. It may well be supposed therefore that there are other cases, perhaps the majority, in which subcutaneous cisterns are present at birth but not large enough or in such a position as to call attention to themselves. In such cases the first indication ofthe abnormality would be the development of vesicles later.
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PATHOGENESIS
As has been stated above there are certain cases in which the natural history strongly suggests that the primary and congenital component of the L.C. lesion is the deep one. It can therefore be put forward as a hypothesis that the child is born with one or more isolated cisterns in the deep subcutaneous plane, and with an otherwise normal lymphatic system. It is a matter for conjecture as to how the cisterns might arise, but perhaps the most likely possibility is that they represent embryonic lymph sacs which have failed to link up with their fellows. These sacs develop initially in the embryo as separate structures and become interconnected later to form a continuous system of vessels. As has been pointed out before (Peachey et al., 1970) the majority of L.C. lesions are situated in relationship to the base of a hmb and/or that part of the trunk to which it is connected. That is to say they occupy the regions from which limb buds developed in the embryo. It is thought possible that the sequestration of one or more lymph sacs in the embryo may occur at an early stage of limb development, and that once this has occurred the foundation of a future lymphangioma has been laid. Pursuing this hypothesis it could be supposed that a wholly new and abnormal set of superfluous vascular channels, with dilated lumina and hypertrophied walls, grow out from the congenital cistern towards the skin, as a kind of 'blow-out' phenomenon secondary to the pressure created by the pulsation and tone of the muscle coat of the cistern. Such vessels would have no real circulation in them, only at best an ebb and flow, and they could not function as a drainage system for the skin. Therefore to make this hypothesis compatible with the absence of oedema in lymphangiomatous skin it would have to be supposed that in addition to the abnormal, dilated, functionless vessels arising from the cisterns the skin also contains a system of normal lymphatics with proper central connections responsible for its drainage. Observation
(17) Dye was injected intradermally into macroscopically normal skin within an area of L.C. When the subcutaneous tissues were subsequently explored in the quest for cisterns it was observed by the surgeon that there was a normal number of normal sized lymphatics draining dye from the injection site. These ran down through the subcutaneous fat alongside the dilated abnormal lymphatics ofthe L.C. There was no connection between the normal and the abnormal vessels and neither the abnormal vessels nor the cisterns contained dye. Conclusion
Within an area of L.C. there are two intermingled but separate sets of lymphatics, one normal in structure and in its function of draining the skin; the other dilated, hypertrophic and seeming to perform no useful function as a drainage system. THERAPEUTIC IMPLICATIONS
If it is accepted that the primary fault underlying L.C. is the congenital presence of isolated muscular cisterns, and that the abnormal vessels leading from them towards the skin surface are blind outgrowths from the cisterns, formed in response to their tone and pulsation pressure, then this will have two immediate implications concerning therapy. (i) It must be regarded as futile to remove the skin containing the vesicles and a partial thickness of subcutaneous fat containing abnormal and dilated vessels (i.e. the tissue above the arrows in Fig. roa, b) if the cisterns 'feeding' them are left in situ. Following such incomplete excision the original cisterns will simply sprout new abnormal vessels and subsequently give rise to new vesicles, as in Figs 3 and 4.
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(2) If the cisterns are indeed the primary cause of all the more superficial abnormalities it may well prove to be adequate to remove just the cisterns (i.e. the tissue below the arrows in Fig. loa, b) and leave the skin and upper subcutaneous layer intact. If the cisterns arc the driving force behind the development of the other parts of the lesion (as the natural history of certain cases suggests) their removal might allow these other parts to involute. The cosmetic results of this type of selective deep excision, with skin preservation, would clearly be better than those of total radical excision. Excision of all the affected skin and subcutaneous tissue down to the deep fascia would in many cases (e.g. Fig. i) be a mutilating procedure. The high recurrence rate after surgery in the past may to a large extent be attributed to surgeons erring on the conservative side, but misguidedly tending to conserve the most important part of the lesion, the deep part. In nine cases to date surgery has been aimed at removing as many as possible of the cisterns and preserving as much as possible of the overlying skin. Quite small ellipses of skin containing half or much less of all the vesicles present have been excised, the margins of the wounds undercut in all directions and the underlying cisterns located and removed down to the level of the deep fascia. The wounds have then been closed, leaving vesicles still present in the adjacent skin. The results have so far been the exact opposite to those shown in Figs 3 and 4. No new vesicles have formed and those that remained in the skin after operation have disappeared. An account of the longer follow-up of patients treated by this method will be made the subject of a future publication. ACKNOWLEDGMENTS
The author wishes to express his gratitude to the various dermatological and surgical colleagues who in one way or another have steered excision specimens of L.C. into his hands; especially to Professors N.L.Browse and J.B.Kinmonth, without whose assistance this study could not have progressed beyond the armchair stage. Particular thanks are due to Professor Browse for carrying out, at the author's request, the procedures on which observations 16 and 17 were dependent. Theauthor also wishes to thank Mr David Lane A.I.M.L.T. for technical assistance with the histology. Miss June Thorogood A.I.A.T. for photographic assistance and Mrs Ann Cater for secretarial assistance. This work was partly supported by a grant from the Wellcome Trust, for which the author is deeply grateful. REFERENCES KiNMONTH, J.B. (1-972) The lymphatics. Edward Arnold, London. PEACHEY, R.D.G., LIM, C-C. & WHIMSTEB, L W . (1970) Lymphangioma of skin. A review of 65 cases. British Jourjial of Dermatology, 83, 519.
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