Melanocytic schwannoma of the cutaneous and subcutaneous tissues: three cases and a review of the literature

Abstract

Melanocytic schwannoma is a rare soft-tissue tumor, which arises most commonly in the paraspinal sympathetic chain. In general, 25% of the patients develop metastasis. To date, only 17 cases of a cutaneous and subcutaneous melanocytic schwannoma have been reported. None of these patients developed metastasis. Three cases of cutaneous melanocytic schwannoma, diagnosed in our institution are reported. For further literature overview we performed a search on Medline using the terms 'melanocytic schwannoma' or 'melanotic schwannoma' or 'Carney complex' combined with 'skin' or 'cutaneous', for the period 1970-2007. Seventeen patients were described to have melanocytic schwannoma of the skin or subcutaneous tissues. These papers were reviewed for clinical data. Two of the three patients showed metastatic disease, one of them died of disseminated metastases. In contrast, none of the reported cases of cutaneous or subcutaneous melanocytic schwannomas was characterized by a malignant course. The differential diagnosis, especially with regard to malignant melanoma, is made by histology and by its clinical course, which differs from melanoma in its tendency to recur at the site of excision and slow rate of growth. Commonly misdiagnosed as melanoma, this tumor reveals insights into the origin of both melanocytes and Schwann cells. It is likely that the biological bases for melanoma and melanocytic schwannoma differ. It is necessary to differentiate this tumor from melanoma because of the differing prognosis and the association of melanocytic schwannoma with the Carney complex. Owing to the lack of clinical trials, we recommend that patients be treated according to the existing guidelines for melanoma.