Case 18 Female, 50 years. Papule, lower legShow diagnosis & comments
Very small nodular melanoma (with very small naevus remnant)
Yet another very small melanoma. Despite its diminutive size, there are many features pointing to melanoma: abrupt changes in cell type; cell groups is high-grade atypia; somewhat irregular distribution of pigment. There is only a minimal epidermal component, and ascent of atypical melanocytes is absent. Absence of ascent, which is encountered in a minority of melanomas, is an important cause of melanoma underdiagnosis. Scrutiny of the dermal component of a melanocytic lesion is just as important diagnostically as scrutiny of the epidermal part, if present.
Again, there is a very small naevus remnant within the dermis. Some studies have indicated than naevus cell remnants are more commonly identified in association with small and thin melanomas than with large and thick ones.The most trivial, but in my opinion not implausible, explanation seems to be that they more easily escape recognition in the latter situation.
Sagebiel RW. Melanocytic nevi in histologic association with primary cutaneous melanoma of superficial spreading and nodular types: effect of tumor thickness. J Invest Dermatol. 1993; 100: 322S-325S.