Lentiginous melanoma.

CONTEXT: Atypical lentiginous melanocytic lesions, particularly in older individuals, continue to pose a diagnostic challenge. Such lesions often show features intermediate between lentiginous nevus and melanoma in situ. We have recently defined within this group of lesions a histologic pattern of lentiginous melanoma, a slowly progressing variant of melanoma typically found on the trunk and proximal extremities of middle-aged and older individuals.
OBJECTIVE: To review the clinical and histologic features of lentiginous melanoma and its histologic differential diagnosis. DATA SOURCES: Review of pertinent published literature and work in our laboratory.
CONCLUSIONS: Lentiginous melanoma defines a subset of slowly progressing melanoma occurring in middle-aged and older patients. It is histologically characterized by a broad atypical lentiginous growth pattern of moderately atypical melanocytes showing focal nesting and pagetoid spread without significant dermal fibroplasia or alteration of the rete ridges. Lentiginous melanoma shows significant overlap in clinical and histologic features with atypical lentiginous nevus (of the elderly). Relationship between these entities requires further investigations. Given the risk of progression to invasive melanoma, all lesions showing features of lentiginous melanoma should be treated with adequately wide excision.