Malignant melanoma with unknown primary lesion. Malignant melanoma of which primary lesion could not be confirmed because tumor developed on the right axilla.

A case of malignant melanoma with unknown primary site was reported. The patient was a 59-year-old man, who first noticed on September, 1993, an asymptomatic firm nodule about 3cm in diameter in his right axillar region. As the tumor increased in size, he became aware of erythematous change of the overlying skin, itching, pain and general fatigue. On April, 1994, the patient visited a division of surgery in a general hospital, and he was diagnosed as having malignant melanoma by incisional biopsy of the tumor. Then he was consulted to our department of Dermatology, University of Tsukuba Hospital. Physical examination revealed a large and firm subcutaneous nodule about 6cm in diameter at the right axilla accompanying dark erythematous and edematous change of the overlying skin. There were no findings suggestive for primary melanoma in the perianal, genital, oral or ocular mucocutaneous regions. The patient had no past history of previous operation for any eye diseases, moles or birthmarks, either. Even extensive examinations only detected a few small metastatic lymph nodes around the large tumor. We diagnosed the patient as a case of malignant melanoma with unknown primary site. The tumor was excised with a wide dissection of the overlying skin and a radical right axillar dissection on 35 days after the incisional biopsy. The patient took chemotherapy with CDDP, DTIC and VDS five times. He has been free from the disease for 25 months since the diagnosis was made.