Six cases of metastatic malignant melanoma with apparently occult primary lesions.

We report here six cases of malignant melanoma in which metastatic lesions were detected first. Of these, two cases showed some peculiar features: one exhibited widespread subcutaneous bleeding, probably due to venous rupture, and the other case had a rare primary lesion on the penis. In the Japanese literature, there have been 46 cases of malignant melanoma in which metastatic lesions were detected prior to the initial ones. The preferential site for metastasis was the lymph node (32 cases). The primary lesion was unknown in 35 patients. The outcomes were available for 36 of the 46 patients; 23 died, including 18 who died within two years.