Blue nevus-like melanoma: A rare entity.

Abstract

A 34-year-old man from Guinea-Bissau presented with a rapidly growing tumor on his right foot over 6 months, arising from a long-standing pigmented papule present for more than 20 years. Clinical examination revealed an exophytic black tumor with ipsilateral inguinal lymphadenopathy. Histopathological analysis showed an epithelioid and fusiform melanocytic proliferation in the dermis with abundant melanin. Immunohistochemical staining demonstrated diffuse positivity for Sox-10, Melan-A, HMB45, and PRAME. A diagnosis of blue nevus-like melanoma (BNM) was confirmed. BRAF V600 mutation testing on a cutaneous metastasis was negative. Staging imaging revealed widespread metastases involving lymph nodes, brain, lungs, liver, stomach, duodenum, colon, adrenal glands, pancreas, gallbladder, and bones. Despite 4 cycles of ipilimumab/nivolumab immunotherapy, the disease progressed, and the patient died 4 months after diagnosis. BNM is a rare melanoma variant, often arising from a pre-existing blue nevus, with aggressive potential and frequent lymph node metastasis. The molecular heterogeneity of BNM and the limited therapeutic options underscore the need for further research into targeted therapies and prognostic biomarkers for this rare melanoma subtype.