Case 8 Female, 50 years, p16LEIDEN germline mutation. Multicoloured macule of 5 mm, skin of calf regionShow diagnosis & comments
Very small superficial spreading melanoma
This is very small lesion shows cellular atypia; ascent of atypical melanocytes; compact clustering of atypical dermal melanocytes into rounded small nests; a mild fibroinflammatory response; a very small dermal naevus remnant that constrasts with the nested atypical melanocytes (last micrograph of this series).
Such very small melanomas are most commonly derived from patients with a history of previous melanoma, or family members of a melanoma risk family, such as this one (p16Leiden is an inactivating mutation of the p16 tumour suppressor gene that runs in some families in the West of the Netherlands, and is associated with the familial dysplastic naevus syndrome). Close surveillance, with whole body photographs, leads to identification and removal of small changing irregular pigmented lesions, some of which turn out to be small melanomas.
There is a risk of melanoma overdiagnosis when very small lesions are removed from melanoma patients or their family members. Such overdiagnosis would explain why second melanomas are far more commonly detected in the first few years after removal of the initial melanoma, a phenomenon that is difficult to explain if the lesions are independent of each other. Also, individuals seeking medical attention because of a melanoma that has occurred in their family, may have small lesions removed which, when diagnosed as small melanoma, might result in a family tree that indicates familial melanoma risk.
It is therefore wise to refrain from heorism when confronted with a tiny and slightly irregular lesion, and issue a verdict of MELTUMP (melanocytic tumor of uncertain malignant potential) rather than small melanoma, whenever the histological features are not entirely conclusive. In the present instance, however, I feel the features are indicative of melanoma.
van der Rhee JI, Mooi WJ, Kukutsch NA, de Snoo FA, Bergman W. Iatrogenic melanoma. Comment on: Melanoma epidemic: a midsummer night's dream? Br J Dermatol. 2010; 162: 457-8.