[Metastatic melanoma of unknown primary site]

Melanomas of unknown primary site are rare. To establish their diagnosis the metastatic nature of the lesion must be confirmed clinically and histologically, the melanoid nature by histology and immunohistochemistry. Any primary melanoma must be eliminated by careful examination of the skin and mucosa, and the absence of past surgical excision of skin lesions must be confirmed. We studied the epidemiological, clinic and prognostic characteristics of 19 melanomas of unknown primary site in a series of 646 melanomas.

This retrospective study was conducted on a series of 646 melanomas recruited over a period of 14 years. The epidemiological (age, gender, phototype and family history of melanoma), clinical and prognostic parameters (relapse and global survival rate) were analyzed in 19 patients. Clinical and epidemiological data were compared with the 646 melanomas of the series. The prognostic parameters were compared with the melanomas of the series at the same stage.

The melanomas with unknown primary site represented 2.94 p. 100 of our series and concerned 10 men and 9 women with a median age of 60 years. Eight patients presented stage III melanomas, according to MD Anderson's classification and 11 stage IV. Relapse after surgery was observed in 63 p. 100 of patients and 9 deceased during the observation period. In stage III patients the probability of survival after 2 years was of 51 p. 100 and for stage IV 34 p. 100.

In our series the frequency of melanomas of unknown primary site is comparable to that observed in other studies. Compared to melanomas of known primary site, there was a preponderance in men and in slightly older patients. There was a majority of single glandular localizations and no particular site was preponderant. Survival of Stage III patients was comparable to that of melanomas of know primary site. However, for stage IV patients it appeared better, as has been noted in other series. Treatment of metastatic melanomas of unknown primary site should therefore be the same as that of classical forms. Whenever possible, surgery remains the first indication. Search for the primary site must be orientated by clinical examination including complete examination of the skin and mucosa (ENT, ophthalmologic and genito-urinary), eventually associated with paraclinical investigations, depending on the symptoms.