THORACIC DUCT CYST: A N UNUSUAL SUPRACLAVICULAR MASS Mark K. Wax, MD, FRCS (C), and Murray E. Treloar, MD, FRCS (C)
Lesions of the thoracic duct may occur either in the neck or the mediastinum. The majority of lesions that present in the neck consist of chylous fistulae and are secondary to neck surgery. Cysts of the thoracic duct are very rare and are usually reported as a disease entity of the mediastinum. There are only two reported cases in the literature of thoracic duct cysts occurring in the neck. The third case of a thoracic duct cyst located primarily in the neck is reported. Thoracic duct cysts in the neck must be differentiated from other cysts of the neck, because not recognizing the inferior attachment to the thoracic duct, may result in the disastrous consequence of a chylothorax. Diagnosis can easily be made by fine-needle aspiration with biochemical analysis. Computerized axial tomography (CAT) is useful in defining the anatomic boundaries. A weakness in the wall of the thoracic duct, either on a congenital or degenerative basis, has been postulated as the etiology. The natural history of these lesions remains unknown. Smaller lesions may be followed at routine intervals. Larger lesions should be surgically removed because of the possible complications that may ensue as a result of traumatic rupture or inflammation. HEAD & NECK 1992;14:502-505 0 1992 John Wiley & Sons, Inc.
From the Department of OtolaryngologyiHead and Neck Surgery (Dr. Wax), West Virginia University, Morgantown, West Virginia; and Department of Pathology (Dr. Treloar), Oshawa General Hospital, Oshawa, Ontario, Canada. Acknowledgments: The authors thank Carol Panepinto for her technical assistance in the preparation of this manuscript and Jim Nelson for providing the CAT scans. Address reprint requests to Dr. Wax at the Department of Otolaryngology/Head 8, Neck Surgery West Virginia University School of Medicine, Health Sciences Center, South, Morgantown, WV 26506. Accepted for publication April 1, 1992.
CCC 0148-6403/92/060502-04 0 1992 John Wiley & Sons, Inc.
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Thoracic Duct Cyst
Cystic dilation of the thoracic duct is a very uncommon entity. As one proceeds superiorly, the incidence of chyle cysts decreases. Cisterna chyli cysts are the most common, thoracic duct cysts of the mediastinum are second, and thoracic duct cysts of the neck are the rarest. There have been only two previous reports in the literature of thoracic duct cysts occurring in the supraclavicular area.'p2 One patient required surgical excision' and one patient was followed for 1.5 years with no surgical intervention.' A recent experience with the third reported supraclavicular cyst of the thoracic duct has led to a review of this entity. A discussion of the diagnosis and management of these masses is presented. CASE REPORT
A 56-year-old man was initially seen by his family physician with a 1-month history of a right neck mass. He had had a previous flu-like illness and noticed the mass while shaving. It rapidly increased in size during the 1-month period but produced no other symptoms. His family physician treated it UnSUCCeSSfUlly with two courses of change Oral antibiotics' The lack Of a in the mass prompted referral. At the time of his initial consultation, an additional pertinent history of 40 packs/years of smoking and moderate ethanol intake was obtained. Initial examination demonstrated a 10-cm supraclavicular lesion in the left side of his neck, deep to the sternomastoid muscle, but bulging anteriorly to the muscle. There was no history of cervical or thoracic trauma. His mucosal surfaces, by
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indirect and fiberoptic laryngoscopy, were entirely normal. An ultrasound scan confirmed the cystic nature of the mass and computerized axial tomography (CAT) (Figure 1) showed that the mass was in continuity with a tubular structure extending into the mediastinum. The suggestion of a cyst arising from the thoracic duct was considered at this time. Although the patient was asymptomatic, it was the authors' opinion that the size of the lesion and its origin were indications for removal. OPERATIVE FINDINGS
A low collar-type incision was performed and subplatysmal skin flaps were elevated in the usual manner. The sternocleidomastoid muscle was identified and the fascia around it freed up in its inferior third. The great vessels (common carotid and jugular vein) were identified and retracted medially. A 10-cm cystic mass was identified lateral to the vessels and followed superiorly. It tapered out into fine strands attached to the internal jugular vein but there was no luminal connection between the cystic structure and the internal jugular vein; therefore, these fine strands were ligated. Inferiorly, the cyst was followed deep to the clavicle into the superior mediastinum where it funneled down to a 0.5- to 1-cm sized duct. This duct was clamped and suture ligated with 2-0 silk, and the cyst was removed from the surgical field. A suction drain was placed. The patient had an uneventful postoperative course and with 3 years of follow-up has had no recurrence or symptoms from the procedure. A CAT
FIGURE 1. CAT demonstrates a large cystic structure deep to the sternomastoid muscle. It displaces the carotid sheath contents in a posterolateral fashion.
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scan obtained 2 years postoperatively showed no change in the appearance of his remaining thoracic duct. The pathology revealed a cyst with a 2-mm thick wall. Microscopically, there was evidence of fibrous thickening of the intima, thinning of the muscle layer, and a patchy infiltrate of lymphocytes and plasma cells. Focal pools of mucosubstance were present. DISCUSSION
Disease entities involving the thoracic duct consist primarily of chylous These may occur as a consequence of neck surgery with radical neck dissection being the most frequent cul~ r i t . However, ~-~ chylous fistula has been described after cervical lymph node biopsy, removal of cervical ribs, as well as after both penetrating and blunt t r a ~ m a . ~Cystic - ~ dilation of the thoracic duct is most commonly reported in the mediastinum. It was first reported in a postmortem study by Enzmann in 1833.6 Emerson in 1950 described the first case diagnosed at surgery.6 T ~ u c h i y a in , ~ 1980, reviewed the eight cases in the literature and added one. Since that time, five more cases have been reported.8-12 There have been only two reports of supraclavicular thoracic duct cysts in the literature.li2 The thoracic duct originates in the abdomen as the cisterna chyli. It then runs superiorly to the right of the midline to the level of T-5 orT-6 where it crosses to the left to run between the aorta and azygos vein.3 It enters the left side of the neck posterior t o the innominate artery and arches 3 to 5 cm above the clavicle running anterior to the phrenic nerve, thyrocervical trunk, and subclavian artery. It lies posterior to the carotid artery, vagus nerve, and internal jugular vein in the majority of cases. Occasionally, it will lie anterior to the inferior jugular vein.13 It then empties into the junction of the left subclavian vein with the left internal jugular vein. The thoracic duct may be as wide as 4 mm but is more commonly 2 to 3 mm in diameter. In general, the duct wall is composed of an endothelial-lined intima, a tunica media, and then adventia. The contribution of these components to the duct wall varies depending on the location. In the thoracic region, the duct wall is relatively thick with a subendothelial layer containing collagenous and elastic fibers with a few longitudinally arranged smooth muscle fibers (Figure 2). This is in contrast to the cervical portion which is made up of a thin subendothelial layer of connective tissue. An internal elastic lumina is
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FIGURE 2. Photomicrograph of the normal thoracic portion of a thoracic duct. Note the very thin layer of intima (small arrow) with normal muscular layers (larger arrow) and an adventival fat layer (double arrow).
present in the thoracic region but is absent in the cervical region. Finally, the thoracic region has a larger quantity of smooth muscle fibers arranged in an uneven fashion when compared to the cervical portion.14 Flow of lymph in the thoracic duct depends on a number of factors. The peristaltic contraction of the duct wall, raised intra-abdominal pressure, respiratory pressure changes, and transmitted pulsations from adjacent vessels all contribute t o the maintenance of lymphatic flow. Although it has been postulated that active peristalsis occurs in the thoracic portion, it is thought that the cervical portion acts more passively.'* Cervical transport is influenced by respiratory pressures with increases in intrathoracic pressure being transmitted across the duct wall and promoting the flow of lymph fluid. The causes of a thoracic duct cyst are considered uncertain. Two etiologies have been postulated. One is a congenital weakness in the wall of the thoracic duct. The second is a degenerative process consisting of inflammatory or atherosclerotic changes in the cyst wall. Weakness of the wall of the thoracic duct will allow for cystic dilation. The histopathology of the case described revealed a patchy infiltrate of lymphocytes with occasional plasma cells throughout the wall of the cyst. There is intimal fibrosis and a marked thinning of the muscular layer. A battery of special stains, including those for mucosubstances and elastic, was performed by our pathologist but were noninformative. In the case described, it was felt that the cyst was due to
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degeneration of the wall, secondary to an inflammatory process. The exact etiology remains unknown. An ultrasound scan of these lesions is helpful in ascertaining the cystic nature but not in defining the inferior extent. CAT, as was demonstrated in this case, can define not only the cystic nature of the lesion but its anatomic connection with the thoracic duct in the mediastinum. This allows for both a definitive diagnosis and the planning of therapy. We have no experience with magnetic resonance imaging (MRI)for the assessment of these lesions. The use of lymphoscintigraphy in the detection of thoracic duct malformations has been described,15 as has lymphography. In each of these cases the contrast material, whether radionuclide or lipiodol, was injected into the dorsal area of the foot. The migration and collection of the contrast material in the cystic structure allowed a diagnosis of thoracic duct cyst. In both of these case^,^"^ when the diagnosis had been made, no further treatment was deemed necessary by the authors. Other authors have used needle aspiration with chemical analysis in conjunction with the location of the cyst to develop a definitive diagnosis.','' The value of fine-needle aspiration must be appreciated. It is a well-accepted diagnostic procedure with low morbidity. In these cysts, the fluid has a higher concentration of fat than normal serum.3 It characteristically is milky white. Chemical and cytologic analysis allows for differentiation from other types of cysts (branchial cleft, thyroid, parathyroid, etc.) that may arise in this area. In this case, the CAT scan was highly suggestive of a thoracic duct lymphocele, and it was felt that no further invasive investigative modalities, such as lymphoscintography or lymphography, should be pursued. Until a report in 1946 by Loe," the drainage of lymph by the thoracic duct was considered to be essential for life. Ligation of the thoracic duct, until that time, was considered incompatible with life. Since that initial report, the thoracic literature has supported the relative lack of morbidity associated with ligation of the thoracic duct. Head and neck surgeons are frequently in the area of the thoracic duct on the left side. If the duct is accidently transected, it is ligated.173-5The morbidity from this is low and acceptable. Of the two cases of supraclavicular thoracic duct cysts previously reported in the literature, one was resected surgically' and one
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had no surgical intervention.' Both patients were followed for a minimum of 3 years with no adverse affects. It is the authors' feeling that a cystic mass of this size, although benign in nature, should be surgically removed. The degenerative changes seen in the wall of this cyst make us concerned that spontaneous or traumatic rupture may occur. This may possibly lead to a chylothorax with its associated morbidity and possible mortality. Although branchial cleft and thyroglossal duct cyst have a significant incidence of infectious complications, this has not been reported in thoracic duct cysts. Due to the constant flow of lymph and a subsequent lack of stagnation, the incidence of infection in these cysts should be very low and not of concern in this disease entity. The surgical removal was readily performed through a transcervical approach with ligation of the distal end of cyst in the mediastinum where it had narrowed down to normal duct size. The morbidity of the procedure was nil. The patient was discharged 2 days following his procedure. Follow-up at 3 years showed no evidence of recurrence and no complications.
REFERENCES
1. Kolbenstvedt A, Aunesan J. Cystic dilation of the thoracic duct presenting as a supraclavicular mass. Br J Radiol 1986;59:1228- 1229.
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2. Barlow D, Gracey L. Cystic dilution of the thoracic duct. Br J Clin Pract 1965;19:101-102. 3. Kassel RN, Haves TE, Gullane PJ. The age of topical tetracycline in the management of persistent chylous fistulae. J Otolargngol 1987;16:174- 178. 4. Thawley SE. Chylous fistula prevention and management. Laryngoscope 1980;90:522-525. 5. Lucente FE, Ltaban DT, Lawson W, et al. Chyle fistula management. Otolaryngol Head Neck Surg 1981;89:575578. 6. Emerson GL. Supradiaphragmatic thoracic duct cyst. N Engl J Med 1950;242:575-578. 7. Tsuchiya R, Sugiura Y, Ogata T, et al. Thoracic duct cyst of the mediastinum. J Thorac Surg 1980;79:856859. 8. Hori 5, Harada K, Morimotu 5, Uchida H, Okumura K. Lymphangiographic demonstration of thoracic duct cyst. Chest 1980;78:652-654. 9. Cohen EB, Kompaniez E. Supradiaphragmatic thoracic duct cyst. N Engl J Med 1962;266:1319-1321. 10. Mizumura S, Ohata M. A case report of thoracic duct cyst with generalized neurofibroma. J Thorac Surg 1968;21: 57-60. 11. Fernandez BB, Broudy NS, Correll N. Supradiaphragmatic cyst of the thoracic duct. Ill Med J 1955;147:365367. 12. Morettia LB, Allen TE. Thoracic duct cyst: diagnosis with needle aspiration. Radiology 1986;161:437438. 13. Greenfield J, Gottlieb, MI. Variations in the terminal portion of the human thoracic duct. A m J Surg 1956;73:955-959. 14. Elzawahry MD, Sayed NM, ElAwedy HM, et al: A study of the gross microscopic and functional anatomy of the thoracic duct and the lymphovenous junction. Znt Surg 1983;68:135- 138. 15. Lopez OL, Rodriguez-Maisano E, Delevuax JL. Thoracic duct malformations lymphoscintigraphic diagnosis. Clin Nuclear Med 1986;11:479-481. 16. Loe RM: Injuries of the thoracic duct. Arch Surg 1946;53: 448-455.
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