[Malignant melanoma evolving inside a cerebral epidermoid cyst].

A case of malignant melanoma arising in a cerebral epidermoid cyst is reported. The neoplasm presented as a rapidly enlarging mass in the left temporal lobe of a 52-year-old woman. The authors provide histological evidence for the provenance to tumour cells from the epithelial lining of the cyst. The melanocytic nature of the neoplasm was demonstrated by immunohistochemistry and electron microscopy. Post mortem examination ruled out the possibility of metastatic origin. The occurrence of intracranial epidermoid cysts and malignant melanoma, their eventual association with maldevelopmental processes or neoplasia are briefly reviewed. Although linked together histogenetically, epidermoid cysts and melanoma do not seem to be involved by common pathogenetic processes. To the best of our knowledge, no previous reference is available on malignant transformation of melanocytes in an epidermoid cyst.