COMMENTARY
INCIDENT LIGHT MICROSCOPY: REFLECTIONS ON MICROSCOPY OE THE LIVING SKIN JURGEN KREUSCH, M.D., PH.D.
"Dermatologists can still learn a great deal by a detailed in vivo examination of the surface of the skin." This statement made by Cunliffe in 1974 referred to microscopic studies of the skin's surface and is still valid. The obvious approach of examining the skin with a microscope has been tried for over 100 years, but has never been introduced as a standard procedure into dermatology. New interest in better diagnostic methods has arisen due to the increasing incidence of malignant melanoma. As the differential diagnosis of pigmented skin lesions can be very difficult, and usually not more than 80% of all melanoma are clinically identified, microscopy of pigmented skin lesions was (re-)discovered as a tool for making a more reliable diagnosis. Microscopy of the skin is, however, helpful in the diagnosis of more tban just pigmented lesions.
cal or physical stimulation. Correctly speaking, the term "incident light microscopy (of the skin)" (ILM) most appropriately describes the technique. The strata of the skin to be examined are not specified, and no incorrect interpretations of the optical phenomena may be construed.
OPTICAL EQUIPMENT
The instrument most widely used is the Heine Delta 10 dermatoscope, which enlarges 10-fold, only a little more than an ordinary magnifying glass. Unfortunately, one has to approach the patient very closely for proper observation. For scientific purposes many investigators have used operating microscopes. They allow stereoscopic viewing of the lesions and photographic documentation, but they are very expensive and difficult to handle. We prefer to use our own hand-held stereomicroscopes, with a magnification range of 20- and 40-fold. They permit a longer working distance and a better perception of tbe three-dimensional structures of a lesion, the impression of a spatial structure being proportional to tbe magnification used. The 40-fold magnification allows recognition of details as small as a single pigment bearing cell 30 |J,m in diameter. Thus the range of observation varies between examination of the entire lesion and visualization of its cellular components, covering the architectural features normally judged by histology. Dermatologists with particular histologic experience are able to "see" the future vertical histological section in vivo as far as the architectural details of the lesion are concerned. Another approach is the use of electronic microscopes, with CCD-chip supported lenses and the possibility of electronic processing and storage of the images.
PRINCIPLE OE THE METHOD
The surface of a lesion reveals a lot of information about the process going on below, but it reflects and disperses most of the incident light, thus preventing scrutinization of underlying details. Application of an oil, preferably liquid paraffin, renders the horny layer of the epidermis translucent, while covering the oil drop with a glass plate yields a horizontal surface further aiding in undisturbed inspection of underlying details. Various structures and colors of a pigmented lesion become visible only under these conditions. Details throughout the epidermis, the stratum papillare and the upper stratum reticulare can be seen under illumination with visible light, provided they reflect or absorb enough light. Current terminology regarding this technique is confusing. Some investigators use terms like "surface," "epiluminescent," or "incident light"-microscopy, others use "dermatoscopy." But in fact, not only the surface of the skin or the dermis are examined, and the term "luminescence" should be most precisely reserved for light emission upon chemi-
DIAGNOSTIC INDICATIONS FOR USE OF ILM
With an incident light microscope, one is able to study pigmented conditions of the skin such as most melanocytic tumors and pigmented variants of epithelial tumors (different types of pigmented keratoses and basaliomas). Furthermore, all lesions containing blood (i.e., hemangiomas and hemorrhages) are easily identifiable.
From tbe Clinic for Dermatology, Medizinische Universitat, Lubeck, Lubeck, Germany. Address for correspondence: Jurgen Kreusch, M.D., Medizinische Universitat Lubeck, Clinic for Dermatology, Ratzeburger AUee 160, D 2400 Lubeck, Germany. 618
Incident Light Microscopy Kreusch
Even in tumors, which do not contain pigment, the blood vessels are visible, and the pattern of vascularization may give valuable clues to the nature of the lesion. For example, basaliomas sbow patterns distinctly different from solar keratoses and spinocellular carcinomas. Some severe conditions, such as scleroderma and dermatomyositis also cause structural and architectural changes in the capillaries of the skin. These are studied best in the nailfold region. ILM of these vessels (nailfold microscopy), therefore, is a method contributing to the rapid assessment of suspected coUagenoses. Parasites, especially Sarcoptes scabiei may represent a difficult diagnostic problem. Tape stripping or removal of a mite witb a needle are insensitive methods and sometimes painful, and tberefore, not well accepted, especially by children. The pigmented thoracic sections of the parasites are, however, clearly visible witb an incident light microscope. Many suspicious sites may be examined within a few minutes without causing any harm or discomfort to the patient. Finally, most foreign bodies in tbe skin (e.g., splinters, stingers) are easily traced, and tbeir complete removal verified.
TOTAL OF ALL PIGMENTED LESIONS
NONMELANOCYTIC LESIONS
MELANOCYTIC LESIONS
1 BENIGN MELANOCYTIC LESIONS
1 MALIGNANT MELANOMA
Figure 1. Diagram showing the basic diagnostic decisions for the identification of malignant melanoma among other pigmented lesions of the skin. Morphologic details as recognized by ILM greatly improve tbe reliability of these decisions.
Using this approach, nearly no melanoma could get lost or misdiagnosed as a seborrheic keratosis or similar harmless lesion. A scoring procedure has been described for the identification of malignant melanoma among the mass of benign melanocytic lesions (unpublished observation). Among the non-melanocytic lesions, further features permit a detailed differentiation.''''-'" The most valuable aspect of ILM is its sensitivity in the detection of malignant melanoma and its specificity in excluding most of the non-melanocytic lesions preventing unneeded treatment for melanoma. Whereas clinical diagnosis detects at best 80% of all melanomas, ILM identifies more tban 90% of all cases prior to surgery.-''" As long as no effective therapy for advanced stages exists, early detection remains the only promising strategy in fighting this tumor. Unfortunately, in my experience the identification of dysplastic nevi is not as reliable. This is not surprising in view of the difficulty in the definition of "dysplasia" of a melanocytic nevus.
MORPHOLOGY OF PIGMENTED SKIN LESIONS
The most important progress achieved through the use of the ILM was the discovery of particular details in pigmented skin lesions, some of which have been shown to be very specific for certain subtypes (e.g., malignant melanoma).^ In general, one may classify tbe details to be visualized into the following categories: those of a lesions surface, those of structure and color of the pigmentation, and those of the vascular pattern. Also important are aspects of the three-dimensional structures, especially of the homogeneity of the architecture. A taxonomic system for a very precise description of pigmented lesions can be defined. A diagnostic pathway may be set up, using dichotomic decisions on basis of the presence or absence of certain criteria. lLM has opened an as yet undescribed access to the morphology of pigmented tumors of the skin and thus offers a valuable aid in making a diagnostic decision. A pathway for the basic diagnostic steps in the detection of malignant melanoma is shown in Figure 1. A detailed and specific description of details in such lesions is essential for their reliable identification. It has been shown that nearly 100% of all pigment bearing melanocytic lesions (e.g., lentigines, nevi, and malignant melanoma) display at least one out of four very characteristic pigment patterns in combination with one of the specific colors of melanin. The pattern most frequently encountered is the so-called pigment network, which may be explained by the distribution of pigment along the dermo-epidermal interface. A search for the combination of a pattern and a color, therefore, is the key to identification of almost all melanocytic lesions.
PERSPECTIVES EOR USE OF ILM
There are two main fields of application for ILM: in the dermatologist's office for better routine diagnosis, and in the field of research. Detection of malignant melanoma at a rate of epidemiologic significance requires an inexpensive, rapid, harmless, but sensitive method for screening many pigmented lesions in many people. Physicians should be able to check their patients' moles at many places, not only at highly specialized centers.'' ILM fulfills most of these requirements. To achieve this, inexpensive instruments must be available, and one sbould be able to learn tbe basic diagnostic technique within a short period. Nomenclature should be standardized to permit communication about findings in pigmented lesions. Attempts in this direction have already been made,' but a variety of nomenclatures for 619
International Journal of Dermatology Vol. 31, No. 9, September 1992
these phenomena are still in use, and no consensus exists as to which details are of diagnostic importance and how they should be named. In my opinion, the missing standardization has prevented many dermatologists from using ILM. We have begun to develop teaching aids (a color atlas and a slide viewing instruction course),'" and the first trials of these have been rather well received. The skin is really an ideal object for in vivo microscopic investigation, being the only living cellular "culture" in our body that is constantly and easily visible. Where else can we observe single cells in their natural environment repeatedly and over a long period, as well as study the structure and function of their nourishing blood vessels? Attempts have been made in the past,^ but only now can optical equipment and staining procedures significantly facilitate examination of living skin. Additional methods of surface analysis (image analysis, profilometry) and measurements of biochemical parameters permit further evaluation of epidermal structures and their metabolism and thus might help to close the gap between biochemistry and immunology at the cellular level and macroscopic observation and morphology of the skin.
Acknowledgment: to English.
Ms. C. Keeler assisted in the translation
REEERENCES 1.
2.
3.
4.
5.
6.
7.
CONCLUSIONS
The increase of information obtainable when viewing the skin at high magnification is always fascinating. What the naked eye just assumes, tbe microscope makes visible. The true nature of many processes becomes obvious. The use of a stereomicroscope adds the visualization of a further dimension. As viewed three dimensionally, the regular network of the dermo-epidermal interface is of a fascinating regularity and beauty. Microscopy of the skin not only satisfies our scientific interests but also our esthetic sensibility. As with each microscopic technique, one should remind the viewer not to get lost in the details, but to integrate them into an overall view.
8.
9.
10.
11.
MacKie RM. Cutaneous microscopy in vivo as an aid to preoperative assessment of pigmented lesions of the skin. Br J Plast Surg 1972; 25:123-129. Fritseh P, Pechlaner R. Differentiation of benign from malignant melanocytic lesions using incident light microscopy. In: Ackerman AB, ed. Pathology of malignant melanoma. New York: Masson, 1981:301. Kreusch J, Rassner G. Strukturanalyse melanozytischer Pigmentmale durch Auflichtmikroskopie. (Structural analysis of melanocytic pigmented lesions using incident light microscopy). Hautarzt 1990; 41:27-33. Kreusch J, Rassner G. Standardisierte auflicbtmikroskopisehe Unterscheidung melanozytischer und nichtmelanozytischer Pigmentmale. (Standardized differentiation between melanocytic and non-melanocytic pigmented lesions using incident light microscopy) Hautarzt 1991; 42:77-83. Pehamberger H, Steiner A, Wolff K. In vivo epiluminescence microscopy of pigmented skin lesions. I. Pattern analysis of pigmented skin lesions. J Am Acad Dermatol 1987; 17:571-583. Soyer HP, Smolle J, Hodl S, et al. Surface microscopy. A new approach to tbe diagnosis of cutaneous pigmented tumors. Am J Dermatopathol 1989; 11:1-10. Steiner A, Pehamberger H, Wolff K. In vivo epiluminescence microscopy of pigmented skin lesions. II. Diagnosis of small pigmented skin lesions and early detection of malignant melanoma. J Am Acad Dermatol 1987; 17:584-59L Koh HK, Lew RA, Prout MN. Screening For melanoma/skin cancer: theoretic and practical considerations. J Am Acad Dermatol 1989; 20:159-172. Bahmer FA, Fritseh P, Kreusch J, et al. Terminology in surface microscopy. J Am Aead Dermatol 1990; 23: 1159-1162. Kreusch J, Rassner G. Auflichtmikroskopie pigmentiereter Hauttumoren. Fin Bildatlas. (Incident light microscopy of pigmented skin tumors). A color atlas. Stuttgart: G. Thieme Verlag, 1991. Goldman L. Direct microscopy of skin in vivo as a diagnostic aid and research tool. J Dermatol Surg Oncol 1980; 6:744-756.
From the collection of "La Pharmacie Fran^aise," New Orleans, Louisiana, Mr. Ben Bavly, Curator. 620
INCIDENT LIGHT MICROSCOPY: REFLECTIONS ON MICROSCOPY OE THE LIVING SKIN JURGEN KREUSCH, M.D., PH.D.
"Dermatologists can still learn a great deal by a detailed in vivo examination of the surface of the skin." This statement made by Cunliffe in 1974 referred to microscopic studies of the skin's surface and is still valid. The obvious approach of examining the skin with a microscope has been tried for over 100 years, but has never been introduced as a standard procedure into dermatology. New interest in better diagnostic methods has arisen due to the increasing incidence of malignant melanoma. As the differential diagnosis of pigmented skin lesions can be very difficult, and usually not more than 80% of all melanoma are clinically identified, microscopy of pigmented skin lesions was (re-)discovered as a tool for making a more reliable diagnosis. Microscopy of the skin is, however, helpful in the diagnosis of more tban just pigmented lesions.
cal or physical stimulation. Correctly speaking, the term "incident light microscopy (of the skin)" (ILM) most appropriately describes the technique. The strata of the skin to be examined are not specified, and no incorrect interpretations of the optical phenomena may be construed.
OPTICAL EQUIPMENT
The instrument most widely used is the Heine Delta 10 dermatoscope, which enlarges 10-fold, only a little more than an ordinary magnifying glass. Unfortunately, one has to approach the patient very closely for proper observation. For scientific purposes many investigators have used operating microscopes. They allow stereoscopic viewing of the lesions and photographic documentation, but they are very expensive and difficult to handle. We prefer to use our own hand-held stereomicroscopes, with a magnification range of 20- and 40-fold. They permit a longer working distance and a better perception of tbe three-dimensional structures of a lesion, the impression of a spatial structure being proportional to tbe magnification used. The 40-fold magnification allows recognition of details as small as a single pigment bearing cell 30 |J,m in diameter. Thus the range of observation varies between examination of the entire lesion and visualization of its cellular components, covering the architectural features normally judged by histology. Dermatologists with particular histologic experience are able to "see" the future vertical histological section in vivo as far as the architectural details of the lesion are concerned. Another approach is the use of electronic microscopes, with CCD-chip supported lenses and the possibility of electronic processing and storage of the images.
PRINCIPLE OE THE METHOD
The surface of a lesion reveals a lot of information about the process going on below, but it reflects and disperses most of the incident light, thus preventing scrutinization of underlying details. Application of an oil, preferably liquid paraffin, renders the horny layer of the epidermis translucent, while covering the oil drop with a glass plate yields a horizontal surface further aiding in undisturbed inspection of underlying details. Various structures and colors of a pigmented lesion become visible only under these conditions. Details throughout the epidermis, the stratum papillare and the upper stratum reticulare can be seen under illumination with visible light, provided they reflect or absorb enough light. Current terminology regarding this technique is confusing. Some investigators use terms like "surface," "epiluminescent," or "incident light"-microscopy, others use "dermatoscopy." But in fact, not only the surface of the skin or the dermis are examined, and the term "luminescence" should be most precisely reserved for light emission upon chemi-
DIAGNOSTIC INDICATIONS FOR USE OF ILM
With an incident light microscope, one is able to study pigmented conditions of the skin such as most melanocytic tumors and pigmented variants of epithelial tumors (different types of pigmented keratoses and basaliomas). Furthermore, all lesions containing blood (i.e., hemangiomas and hemorrhages) are easily identifiable.
From tbe Clinic for Dermatology, Medizinische Universitat, Lubeck, Lubeck, Germany. Address for correspondence: Jurgen Kreusch, M.D., Medizinische Universitat Lubeck, Clinic for Dermatology, Ratzeburger AUee 160, D 2400 Lubeck, Germany. 618
Incident Light Microscopy Kreusch
Even in tumors, which do not contain pigment, the blood vessels are visible, and the pattern of vascularization may give valuable clues to the nature of the lesion. For example, basaliomas sbow patterns distinctly different from solar keratoses and spinocellular carcinomas. Some severe conditions, such as scleroderma and dermatomyositis also cause structural and architectural changes in the capillaries of the skin. These are studied best in the nailfold region. ILM of these vessels (nailfold microscopy), therefore, is a method contributing to the rapid assessment of suspected coUagenoses. Parasites, especially Sarcoptes scabiei may represent a difficult diagnostic problem. Tape stripping or removal of a mite witb a needle are insensitive methods and sometimes painful, and tberefore, not well accepted, especially by children. The pigmented thoracic sections of the parasites are, however, clearly visible witb an incident light microscope. Many suspicious sites may be examined within a few minutes without causing any harm or discomfort to the patient. Finally, most foreign bodies in tbe skin (e.g., splinters, stingers) are easily traced, and tbeir complete removal verified.
TOTAL OF ALL PIGMENTED LESIONS
NONMELANOCYTIC LESIONS
MELANOCYTIC LESIONS
1 BENIGN MELANOCYTIC LESIONS
1 MALIGNANT MELANOMA
Figure 1. Diagram showing the basic diagnostic decisions for the identification of malignant melanoma among other pigmented lesions of the skin. Morphologic details as recognized by ILM greatly improve tbe reliability of these decisions.
Using this approach, nearly no melanoma could get lost or misdiagnosed as a seborrheic keratosis or similar harmless lesion. A scoring procedure has been described for the identification of malignant melanoma among the mass of benign melanocytic lesions (unpublished observation). Among the non-melanocytic lesions, further features permit a detailed differentiation.''''-'" The most valuable aspect of ILM is its sensitivity in the detection of malignant melanoma and its specificity in excluding most of the non-melanocytic lesions preventing unneeded treatment for melanoma. Whereas clinical diagnosis detects at best 80% of all melanomas, ILM identifies more tban 90% of all cases prior to surgery.-''" As long as no effective therapy for advanced stages exists, early detection remains the only promising strategy in fighting this tumor. Unfortunately, in my experience the identification of dysplastic nevi is not as reliable. This is not surprising in view of the difficulty in the definition of "dysplasia" of a melanocytic nevus.
MORPHOLOGY OF PIGMENTED SKIN LESIONS
The most important progress achieved through the use of the ILM was the discovery of particular details in pigmented skin lesions, some of which have been shown to be very specific for certain subtypes (e.g., malignant melanoma).^ In general, one may classify tbe details to be visualized into the following categories: those of a lesions surface, those of structure and color of the pigmentation, and those of the vascular pattern. Also important are aspects of the three-dimensional structures, especially of the homogeneity of the architecture. A taxonomic system for a very precise description of pigmented lesions can be defined. A diagnostic pathway may be set up, using dichotomic decisions on basis of the presence or absence of certain criteria. lLM has opened an as yet undescribed access to the morphology of pigmented tumors of the skin and thus offers a valuable aid in making a diagnostic decision. A pathway for the basic diagnostic steps in the detection of malignant melanoma is shown in Figure 1. A detailed and specific description of details in such lesions is essential for their reliable identification. It has been shown that nearly 100% of all pigment bearing melanocytic lesions (e.g., lentigines, nevi, and malignant melanoma) display at least one out of four very characteristic pigment patterns in combination with one of the specific colors of melanin. The pattern most frequently encountered is the so-called pigment network, which may be explained by the distribution of pigment along the dermo-epidermal interface. A search for the combination of a pattern and a color, therefore, is the key to identification of almost all melanocytic lesions.
PERSPECTIVES EOR USE OF ILM
There are two main fields of application for ILM: in the dermatologist's office for better routine diagnosis, and in the field of research. Detection of malignant melanoma at a rate of epidemiologic significance requires an inexpensive, rapid, harmless, but sensitive method for screening many pigmented lesions in many people. Physicians should be able to check their patients' moles at many places, not only at highly specialized centers.'' ILM fulfills most of these requirements. To achieve this, inexpensive instruments must be available, and one sbould be able to learn tbe basic diagnostic technique within a short period. Nomenclature should be standardized to permit communication about findings in pigmented lesions. Attempts in this direction have already been made,' but a variety of nomenclatures for 619
International Journal of Dermatology Vol. 31, No. 9, September 1992
these phenomena are still in use, and no consensus exists as to which details are of diagnostic importance and how they should be named. In my opinion, the missing standardization has prevented many dermatologists from using ILM. We have begun to develop teaching aids (a color atlas and a slide viewing instruction course),'" and the first trials of these have been rather well received. The skin is really an ideal object for in vivo microscopic investigation, being the only living cellular "culture" in our body that is constantly and easily visible. Where else can we observe single cells in their natural environment repeatedly and over a long period, as well as study the structure and function of their nourishing blood vessels? Attempts have been made in the past,^ but only now can optical equipment and staining procedures significantly facilitate examination of living skin. Additional methods of surface analysis (image analysis, profilometry) and measurements of biochemical parameters permit further evaluation of epidermal structures and their metabolism and thus might help to close the gap between biochemistry and immunology at the cellular level and macroscopic observation and morphology of the skin.
Acknowledgment: to English.
Ms. C. Keeler assisted in the translation
REEERENCES 1.
2.
3.
4.
5.
6.
7.
CONCLUSIONS
The increase of information obtainable when viewing the skin at high magnification is always fascinating. What the naked eye just assumes, tbe microscope makes visible. The true nature of many processes becomes obvious. The use of a stereomicroscope adds the visualization of a further dimension. As viewed three dimensionally, the regular network of the dermo-epidermal interface is of a fascinating regularity and beauty. Microscopy of the skin not only satisfies our scientific interests but also our esthetic sensibility. As with each microscopic technique, one should remind the viewer not to get lost in the details, but to integrate them into an overall view.
8.
9.
10.
11.
MacKie RM. Cutaneous microscopy in vivo as an aid to preoperative assessment of pigmented lesions of the skin. Br J Plast Surg 1972; 25:123-129. Fritseh P, Pechlaner R. Differentiation of benign from malignant melanocytic lesions using incident light microscopy. In: Ackerman AB, ed. Pathology of malignant melanoma. New York: Masson, 1981:301. Kreusch J, Rassner G. Strukturanalyse melanozytischer Pigmentmale durch Auflichtmikroskopie. (Structural analysis of melanocytic pigmented lesions using incident light microscopy). Hautarzt 1990; 41:27-33. Kreusch J, Rassner G. Standardisierte auflicbtmikroskopisehe Unterscheidung melanozytischer und nichtmelanozytischer Pigmentmale. (Standardized differentiation between melanocytic and non-melanocytic pigmented lesions using incident light microscopy) Hautarzt 1991; 42:77-83. Pehamberger H, Steiner A, Wolff K. In vivo epiluminescence microscopy of pigmented skin lesions. I. Pattern analysis of pigmented skin lesions. J Am Acad Dermatol 1987; 17:571-583. Soyer HP, Smolle J, Hodl S, et al. Surface microscopy. A new approach to tbe diagnosis of cutaneous pigmented tumors. Am J Dermatopathol 1989; 11:1-10. Steiner A, Pehamberger H, Wolff K. In vivo epiluminescence microscopy of pigmented skin lesions. II. Diagnosis of small pigmented skin lesions and early detection of malignant melanoma. J Am Acad Dermatol 1987; 17:584-59L Koh HK, Lew RA, Prout MN. Screening For melanoma/skin cancer: theoretic and practical considerations. J Am Acad Dermatol 1989; 20:159-172. Bahmer FA, Fritseh P, Kreusch J, et al. Terminology in surface microscopy. J Am Aead Dermatol 1990; 23: 1159-1162. Kreusch J, Rassner G. Auflichtmikroskopie pigmentiereter Hauttumoren. Fin Bildatlas. (Incident light microscopy of pigmented skin tumors). A color atlas. Stuttgart: G. Thieme Verlag, 1991. Goldman L. Direct microscopy of skin in vivo as a diagnostic aid and research tool. J Dermatol Surg Oncol 1980; 6:744-756.
From the collection of "La Pharmacie Fran^aise," New Orleans, Louisiana, Mr. Ben Bavly, Curator. 620
