Superficial spreading melanoma arising in a congenital melanocytic nevus
Melanoma cells (top) and nevus cells (bottom)
1. Friedman RJ, Rigel DS, Kopf AW, et al.: Favorable prognosis for malignant melanomas associated with acquired melanocytic nevi. Arch Dermatol 119: 455-462,1983.
2. Urso C, Giannotti V, Reali UM, et al.: Spatial association of melanocytic naevus and melanoma. Melanoma Res 1: 245-249,1991.(Download PDF [2.46 MB]).
3. Urso C, Bondi R: The histologic spectrum of acquired nevi. An analysis of the intraepidermal melanocytic proliferation in common and dysplastic nevi. Path Res Pract 190:609-614,1994
The histologic diagnosis of pigmented lesions of the skin is difficult, because many nevi simulate melanoma, some melanomas simulate nevi and because morphologically ambiguous lesions do exist. Moreover, melanocytic nevus and malignant melanoma, the two major entities facing in the field, are not mutually exclusive. They, in fact, may be observed histologically associated, posing diagnostic doubts and pathogenetic questions. The distinction between melanoma cells and nevus cells is often difficult, because small cell melanomas may be found and because nevi sometimes show alarming cytological atypias [1]. Moreover, the association melanoma-nevus poses the problem concerning the relationship existing between the two lesions. Available data concerning the frequence of such an event are variable; however, more frequently, values are about 20-30%.These values are too high to consider the event as fortuitous and speak in favor of a causal specific relation of the type precursor-neoplasia [2]. Analizing a series of primary cutaneous melanomas, some histological characteristics of melanoma associated with a melanocytic nevus emerge: the tumor is almost always a superficial spreading melanoma, tends to be less than 1.50 mm in thickness, shows a low rate of in situ cases, is frequently multiple. Moreover, considering the rate of association melanoma-nevus in respect to Breslow index, it is possible to record a decrease of the value of association as melanoma thickness increases. Such an observation underlines the importance of the time in the process and suggests the existence of a special category of melanomas which arised in a preexisting nevus, but in which the underlying benign lesion is no more evident (apparently de novo melanomas). Melanoma in nevus finally poses the problem of the identification of nevi implying an increased melanoma risk. After the failure of the concept of dysplastic nevus as clinicopathologic entity and as histological entity [3], it is to be cleared if lesions implying an increased risk are histologically identifiable. Meanwhile, a prudent approach may be opportune, using a descriptive diagnosis of nevi, which, indicating the lesion type (junctional, compound, dermal), at the same time specifies the histological features (analityc diagnosis).
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Melanoma (left) associated with a nevus (right)
The other pages
- Home Page: Dermatopathology - C. Urso, MD
- page 1: Melanoma of the skin
- page 2: Histologic diagnosis of cutaneous melanoma
- page 3: Melanoma arising in a melanocytic nevus
- page 4: Infiltration and pseudoinfiltration
- page 5: Sweat gland carcinomas
- page 6: The sentinel lymph node in cutaneous melanoma
- page 7: Bullous cutaneous diseases
- page 8: Spitz nevus
- page 9: Prognostic factors in cutaneous melanoma
- page 10: The dysplastic nevus
- page 11: Dermatofibrosarcoma protuberans
- page 12: Melanoma in situ
- last page: Questions, comments and opinions
page 13: Merkel cell carcinoma
page 14: Basal cell carcinoma
page 15: Melanoma in paediatric age