Amelanotic malignant melanoma where primary lesion was discovered 5 years after metastasis in the lymph node.

A 53-year-old Japanese man presented with a subcutaneous nodule in his left inguinal region in 2002. He was diagnosed as having a malignant tumor of the soft tissues at a local hospital; however, an exact diagnosis was not obtained. CYVADIC (cyclophosphamide, vincristine, doxorubicin, and dacarbazine) therapy was done for adjuvant therapy. In 2004, he noticed a nodule on the left heel. Positron emission computed tomography showed abnormal up-take and he consulted our department. He was diagnosed as having amelanotic malignant melanoma and the lesion was resected. There were no metastases in the groin or popliteal lymph nodes. After the evaluation, the tumor was staged at pT3b N1b M0 stage IIIC (Breslow's tumor thickness was 7 mm). In our hospital, we have experienced 16 cases of amelanotic malignant melanoma. Generally, it is reported that the patients with amelanotic malignant melanoma have a poor prognosis, but we have observed no difference in the outcome between the patients with amelanotic malignant melanoma and those with malignant melanoma.