Giant Pigmented Nevi, Melanoma, and Leptomeningeal Melanocytosis

Abstract

In this study of 55 patients with giant pigmented nevi, special attention has been paid to the clinical features of the nevi, and to the histopathological features present in the biopsy specimens available from all 55 of the patients. The overlapping and mixed nature of the microscopic changes in any single lesion is notable (nevus cells, Schwannian cells, dermal melanocytes). The clinical and sometimes microscopic similarity to neurofibroma is noted. However, we consider giant pigmented nevi and neurofibromatosis to be separate and distinct entities. Review of tissue and clinical material strongly suggests that malignancy, when it does occur, is not always related to an epithelial origin. There are 39 patients reported with melanoma developing in an extensive nevus, but from these patients, no true incidence of malignancy can be ascertained. Epilepsy and other mental and neurological changes may be related to leptomeningeal involvement, particularly in those cases in which giant nevi involve the neck and scalp. There are 20 reported patients with leptomeningeal melanocytosis, some of whom died from hydrocephalus and primary melanoma. The nevus cells in the leptomeninges and in the skin are similar in appearance and staining properties.