Melanoma is a malignant proliferation of melanocytes that has the potential to metastasize. Although the word malignant is commonly used together with melanoma, we prefer to use just the term melanoma throughout this text, because no benign melanoma exists, and the name malignant melanoma is redundant. Melanoma in situ refers to the stage at which the neoplasm is situated within the epidermis and/or epithelium of hair follicles or sweat ducts [Maize 1998]. Thus, since the melanocytes of a melanoma in situ are not present in the dermis and there is no continuity at all with the vascular plexus, a melanoma in situ should, at least theoretically, have no potential to metastasize. The incidence of melanoma has increased significantly over the last decades, but fortunately the prognosis has continued to improve because patients are presenting at an earlier stage with smaller and thinner, potentially curable lesions [Shafir 1982]. Still today, despite progress in the treatment of melanoma, the ultimate goal for physicians is to diagnose melanoma in its early evolutionary phases.

Clinical features

The clinical features of melanomas are protean, reflecting the relatively low sensitivity values in the clinical diagnosis of melanoma that range from 67% to 91% [Wolf 1998]. Melanoma in situ and early invasive melanoma are usually small, more or less irregularly shaped and outlined macules or slightly elevated plaques with pigmentation that varies from pink to dark brown. Obviously, the clinical differentiation from Clark nevi is often difficult even for well-trained dermatologists. Invasive melanomas are, as a rule, papular or nodular, often ulcerated and characteristically exhibit shades of brown and black, but also foci of red, white, or blue coloration. Sometimes they are skin-colored without any brownish-black pigmentation, then being called amelanotic melanomas. Wolf et al. based on a retrospective study of 44,258 histopathologically examined skin neoplasms including 529 melanomas, have recently demonstrated that thick melanomas (Breslow index >4mm) may even have a lower sensitivity of 64.8% compared to melanoma in situ which had a sensitivity of 72.8% [Wolf 1998]. Additionally, paramount for the diagnosis is the patient’s history of changes in size, color and shape or whether any sign of ulceration or spontaneous bleeding was observed. These comments have to be taken seriously and represent a useful extension of the clinical judgment [Kittler 1999].

Dermoscopic features

Dermoscopic criteria for the diagnosis of melanoma, also called melanoma-specific criteria, have been first elaborated and then tested for their diagnostic validity by several authors during the last few years [Argenziano 1998, Kenet 1993, Menzies 1995 and 1996, Oguchi 1998, Pehamberger 1993, Schiffner 2000, Soyer 1995, Steiner 1987 and 1993, Stolz 1994, Wolf 1997].

In order to better systematize these criteria, in Table 1 we have listed the melanoma-specific criteria for the three main anatomic sites, namely, trunk/extremities, face, palms and soles (See Table 1).

In Table 2 the dermoscopic criteria for intermediate and thick melanomas (Breslow index >0.75mm) are summarized because the preformed anatomic structures responsible for the site-specific dermoscopic appearance are destroyed by thick melanomas and thus the dermoscopic features in these melanomas are basically independent of the various sites [Argenziano 1997] (See Table 2).

Table 1.

Melanoma-specific criteria for melanoma in situ and early invasive melanoma (Breslow index <0.76 mm) according to the three main anatomic sites
Anatomic site Criterion Description Frequency of criteria*
Trunk and extremities Multicomponent pattern Combination of three or more distinctive dermoscopic structures Very common
Atypical pigment network Brown to black network with irregular meshes and thick lines Very common
Irregular dots/globules Black, brown, and/or gray round to oval, variously sized structures irregularly distributed within the lesion common
Irregular streaks Irregular, more or less confluent, linear structures not clearly combined with pigment network lines common
Irregular pigmentation Black, brown, and/or gray pigmented areas with irregular shape and/or distribution Common
Regression structures White areas (white scarlike areas) and blue areas (gray-blue areas, peppering, multiple blue-gray dots) may be associated, thus featuring so-called blue-whitish areas virtually indistinguishable from blue-whitish veil Rather common
Blue whitish veil Confluent, gray-blue to whitish-blue diffuse pigmentation associated with pigment network alterations, dots/globules and/or streaks Uncommon

 

Anatomic site Criterion Description Frequency of criteria*
Face Reticular pattern Diffuse pigmentation of the epidermis or the papillary dermis in facial skin reveals a peculiar pattern, also called pseudonetwork, dermoscopically composed of round, equally sized meshes corresponding to pre-existing follicular ostia Always present
Atypical pigment pseudonetwork This is typified by different morphologic aspects of the pseudonetwork due to the different steps of melanoma progression Always present
- Annular-granular structures Multiple blue-gray dots surrounding the follicular ostia with an annular granular appearance Common in the early phase
- Gray pigment network Gray pigmentation surrounding the follicular ostia formed by the confluence of annular-granular structures Common
-Rhomboidal structures Gray-brown pigmentation surrounding the follicular ostia with a rhomboidal appearance Common
Irregular pigmentation Black, brown, and/or gray pigmented areas with irregular size and shape, unevenly distributed throughout a lesionl Rather common not in early phase
Irregular dots/globules Black, brown, and/or gray round to oval, variously sized and shaped structures irregularly distributed within the lesion Rather common

 

Anatomic site Criterion Description Frequency of criteria*
Palms and soles Parallel-ridge pattern Pigmentation aligned along the cristae superficiales. It has to be differentiated from parallel-furrow pattern following the sulci superficiales (common finding in acral nevi) Very common
Irregular dots/globules Black, brown, and/or gray round to oval, variously sized structures irregularly distributed within the lesion Common
Irregular pigmentation Black, brown, and/or gray pigmented areas with irregular size and shape and uneven distribution Common
Irregular streaks Irregular, more or less confluent, linear structures not clearly combined with pigment network lines Rather common
Blue whitish veil Confluent, gray-blue to whitish-blue diffuse pigmentation associated with pigment network alterations, dots/g̣obules and/or streaks Uncommon

 

(*) Very common: >70%; common: 50-70%; rather common: 30-50%; uncommon: <30%

 

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Table 2.

Melanoma-specific criteria for intermediate and thick melanomas (Breslow index >0.75 mm)
Criteria Description Frequency of criteria*
Blue-whitish veil Confluent, gray-blue to whitish-blue diffuse pigmentation associated with pigment network alterations, dots/globules and/or streaks Very common
Irregular dots/globules Black, brown, and/or gray round to oval, variously sized structures irregularly distributed within the lesion Common
Irregular pigmentation Black, brown, and/or gray pigmented areas with irregular size and shape, unevenly distributed  Common
Irregular streaks Irregular, more or less confluent, linear structures not clearly combined with pigment network lines Common
Atypical pigment network Brown to black network with irregular meshes and thick lines Rather common
Vascular pattern Dotted, linear irregular, and/or hairpin vessels Rather common
Regression structures White areas (white scarlike areas) and blue areas (gray-blue areas, peppering, multiple blue-gray dots) may be associated, thus featuring so-called blue-whitish areas virtually indistinguishable from blue-whitish veil Uncommon
Red globules Oval, quite well circumscribed globules with a milky red coloration commonly arranged in small clusters Uncommon

 

(*) Very common: >70%; common: 50-70%; rather common: 30-50%; uncommon: <30%

 

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