EXTRAVENTRICULAR NEOPLASMS WITH NEUROCYTOMA FEATURES - A CLINICOPATHOLOGICAL STUDY OF 11 CASES

The clinicopathological features of a series of neuronal and mixed neu ronal and astrocytic neoplasms of the CNS are described. Patients were aged 5 to 63 years. Six cases were composed predominantly of small ro und cells with clear cytoplasm resembling central neurocytoma but lack ed the characteristic intraventricular location of that tumor. The rem aining five cases had similar neurocytomatous features associated with a benign astrocytic component. Ganglion cells and hyalinization vesse ls were observed in both groups. The growth fraction evaluated with mo noclonal antibody Ki67Mib1 was low, ranging from 1 to 1.5%. Immunohist ochemical detection of synaptophysin played a crucial role in identify ing the neuronal nature of these neoplasms and was instrumental in dis tinguishing them from oligodendrogliomas, with which they are readily confused. The neuronal nature of the oligodendroglial-like cells was c onfirmed ultrastructurally in one case. The present cases, together wi th others reported previously, suggest that neoplasms of the CNS with ''neurocytic'' components are more frequent than generally assumed and expand the morphologic spectrum of neuronal and mixed neuronal-glial tumors. Except for one patient who died postoperatively, all patients were alive at follow-up ranging from 6 to 80 months.