A 57-year-old male patient had a 4×5 cm sized, irregular bordered, dark brownish plaque on the left sole, which has extended gradually since about 1 year ago and showed an occasional bleeding tendency. Laboratory examinations revealed a low hemoglobin level, rouleaux formation on peripheral blood, monoclonal gammopathy of IgG-kappa type and Bence-Jones proteinuria. Bone marrow aspiration findings showed markedly increased immature plasma cells suggesting multiple myeloma. Histopathologic findings of the skin biopsy from the left sole revealed proliferation of atypical melanocytes.

We performed a surgical excision with a skin graft for malignant melanoma and chemotherapy (melphalan, vincristine and prednisolone) for multiple myeloma.