A Challenging Diagnosis of Primary Cutaneous Melanoma With Rhabdomyosarcomatous Differentiation: A Case Study and Review of the Literature

Abstract: Malignant melanomas can adopt characteristics of nonmelanocytic cells or tissue components, a rare phenomenon called divergent differentiation. Melanoma with rhabdomyosarcomatous differentiation is rare with 19 documented cases in the literature. We describe a 69-year-old man with a cutaneous lesion on his left cheek initially diagnosed as a primary rhabdomyosarcoma. Re-examination of the initial biopsy and the subsequent excision with additional stains and molecular tests revealed primary cutaneous melanoma with rhabdomyosarcomatous differentiation. This case highlights the diagnostic challenges associated with this rare melanoma subtype. A review of the literature follows with emphasis on immunohistochemical findings, molecular studies, and follow-up care.