Clinical aspects of unknown primary melanoma.

Of 980 patients with malignant melanoma treated during the past seven years, 55 (5.6%) were found to have metastatic disease and no detectable primary tumor. Thirty-six of these patients with "unknown primary melanoma" had disease limited to lymph nodes (Stage II), whereas 19 had disseminated melanoma (Stage III). The sex and age distribution of these 55 patients were similar to those of a control group of 86 patients with palpable lymph node metastases from a known primary. The site of lymph node metastases for Stage II patients in each group was similar although unknown primary patients seemed to have slightly more involved lymph nodes. By studying patients with the same stage and similar extent of disease, the prognosis of unknown primary melanoma could be determined and compared to known primary melanoma. The overall recurrence rate of patients with unknown primary was no higher than that of patients with known primary. This observation appeared to be true even when patients were compared with respect to adjuvant immunotherapy. The use of adjuvant immunotherapy appeared to favorably affect recurrence rates among the unknown primary patients. Since the recurrence rate for patients with unknown primary melanoma was no higher than that of patients with known primary melanoma, we advocate aggressive surgical management. The occasional long-term survivor with Stage III unknown primary suggests that judicious surgical intervention may benefit these patients as well.