[Differential diagnosis of occult primary malignant melanoma]

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