Differential diagnosis of occult primary malignant melanoma

Controversy exists in literature about therapy and prognosis of malignant m elanoma of unknown primary site. We investigated frequency, differential di agnosis and follow-up of patients with occult primary malignant melanoma tr eated at the University of Leipzig in 1996. Among 135 patients with maligna nt melanoma (MM) seven were found without known primary. In two of seven ca ses the medical history pointed to regression of primary lesion of skin. In another two cases the diagnosis "melanoma" was changed to "lung cancer" af ter autopsy and in one case there was a relationship to a naevus blue resec ted nine months before. Recurrences or metastases occurred within six month s after therapy. Two patients are still alive free of disease after a follo w up of 33 and 24 months. Five patients died from tumor progression between 2 to 14 months postoperatively. Pitfalls in differential diagnosis and way s to find out the primary are discussed. Patients with unknown primary mali gnant melanoma should be treated similar to those with known primary. Radic al surgery is indicated because it's impossible to determine the prognosis of patients with unknown primary malignant melanoma.