Malignant Melanoma With Rhabdomyosarcomatous Differentiation: A Case Report.

Malignant melanoma may exhibit morphologic characteristics of nonmelanocytic cell or tissue components, a phenomenon termed divergent differentiation. Melanoma with rhabdomyosarcomatous differentiation is rare, with 6 definite cases in adults reported in the literature. The authors describe a 75-year-old man with a cutaneous lesion of the right ear initially diagnosed as malignant melanoma. Three months later, biopsy of a right cervical lymph node showed changes suggestive of rhabdomyosarcoma. Reexamination of the initial skin biopsy with muscle markers confirmed a diagnosis of malignant melanoma with rhabdomyosarcomatous differentiation. This case serves to highlight the diagnostic challenges associated with this rare subtype of melanoma.