Pigmented olfactory neuroblastoma: a new example of melanotic neuroepithelial neoplasm.

The light and electron microscopic features of a pigmented olfactory neuroblastoma are described. The neuroblastic nature of the tumor was confirmed by the demonstration of axons, some of which originated from the neoplastic cells, and by the presence of dense-core vesicles in the perikarya and processes of the tumor cells. The tumor contained a large amount of pigment, most of which had the histochemical reactions of melanin, but some of which had that of lipofuscin. Electron microscopy failed to demonstrate the presence of melanosomes or premelanosomes: the pigment showed some of the features of neuromelanin, although the fine structural appearances were not typical. The pigment was interpreted in this case as presumably representing a modified catecholamine degradation product, perhaps related to lipofuscin. The presence of melanotic pigment in an example of olfactory neuroblastoma, unreported until now, augments the list of neurogenic neoplasms in which an association with melanin formation has been described. The significance of this association in tumors originating from the nervous system or its coverings needs further investigation, as the nature of pigment appears to be heterogeneous. These tumors may contain either melanosomal pigment or pigment identified as neuromelanin (or a related substance), seemingly regardless of the derivation of the pigment-bearing cells.