Acral Lentiginous Melanoma, Indolent Subtype Diagnosed by En Bloc Excision: A Case Report

Nail unit melanoma is a type of acral lentiginous melanoma and requires histopathologic examination for a confirmed diagnosis. However, inadequate biopsy techniques make definitive diagnosis difficult. A 61-year-old man presented with progressive nail pigmentation for 15 years, which was clinically highly suspicious for malignancy. Acral lentiginous melanoma was not detected in punch and longitudinal biopsy specimens, but en bloc excision tissue revealed melanoma. Acral lentiginous melanoma is known to have a heterogeneous pathologic manifestation depending on the pigmented region and the time it takes to progress. In this regard, en bloc excision can be considered as a first-line biopsy technique to diagnose acral lentiginous melanoma, indolent subtype.