Metastatic rhabdoid melanoma: report of a case with a comparative review of the literature.

Melanoma has a propensity to mimic the morphologic appearances of a wide variety of epithelial and soft tissue neoplasms. Although rarely encountered, these unusual morphologic variants of melanoma are often treacherous and may be difficult and challenging to diagnose. Thus, recognition of these variants is of paramount importance in the evaluation of any kind of epithelial or soft tissue neoplasm. Rhabdoid melanoma is one such example of these melanoma variants. Very few cases of rhabdoid melanoma have been reported, most of which were found in metastatic lesions. We wish to expand this rather sparse body of literature by reporting a case of metastatic rhabdoid melanoma arising subcutaneously in the right thigh of a 64-year-old man with a remote history of primary toe melanoma. Moreover, we present a comparative review of the clinical, histologic, immunohistochemical and ultrastructural features of previously reported cases. We found significant heterogeneity in the extent of rhabdoid change, expression of melanocytic and non-melanocytic markers and ultrastructural filamentous patterns in the cases we reviewed. It is our hope that this case report and literature review will help pathologists in the evaluation of neoplasms with rhabdoid morphology.