Primary melanocytomas of the spinal cord: a report of seven cases.

Seven cases of primary intramedullary melanocytomas of the spinal cord are reported with clinical features, light microscopy, immunohistochemistry, and ploidy analysis. The patients ranged in age from 24 to 74 years. The tumors were composed predominately of spindle cells with focal aggregates of epithelioid cells. The nuclei were round to oval with variably prominent nucleoli. The tumors contained variable amounts of melanin pigment. Immunohistochemical staining with HMB 45 was positive in 5 cases and negative in 2. None of the tumors was immunoreactive for epithelial membrane antigen (EMA). The clinical outcome ranged from death at 9 days following surgery to 4-year survival without recurrence. The tumors were compared with 5 metastatic melanomas and were found to have a markedly different histology, S phase fractions, and proliferation indices. The categorization of the primary pigmented lesions of the CNS is further discussed in the context of dermatopathologic nomenclature. These 7 tumors appear to be a type of primary central nervous system neoplasm which lacks markedly anaplastic features and exhibits locally aggressive behavior.