Coexistence of amelanotic melanoma and liposarcoma.

An amelanotic malignant melanoma is characterized by little or no pigment. It is frequently misdiagnosed because it is a rare entity in general, and because of its unusual clinical features. Liposarcoma is one of the most common adult soft tissue sarcomas. We encountered a case of amelanotic melanoma with a concurrent liposarcoma. A 68-year-old man presented with a single, 1.5x1.5 cm round erythematous, eroded nodule on the left heel. A biopsy specimen showed atypical, pleomorphic tumor cells with little melanin pigment. The tumor cells were positive for S-100, HMB-45 and negative for cytokeratins. These findings were consistent with amelanotic melanoma. On positron emission tomography/computed tomography (PET/CT), a hypermetabolic lesion was found in the left buttock. This lesion was excised and diagnosed as a well-differentiated liposarcoma. An association between sarcomas and other primary malignancies has been reported. However, an association between melanoma and liposarcoma is rare.