A distinctive glioneuronal tumor of the adult cerebrum with neuropil-like (including "rosetted") islands - Report of 4 cases

Four examples of a novel glioneuronal neoplasm are presented. All turners a ffected adults (including two males and two females aged 25-40 years) as su pratentorial, cerebral hemispheric masses with associated seizure activity and, in one case, symptoms of raised intracranial pressure and progressive hemiparesis. CT scans in two cases revealed hypodense masses without calcif ication. MRI scans at presentation demonstrated, in all cases, solid T-1-hy perintense and T-2-hyperintense turners with mass effect in one instance bu t no edema or contrast enhancement. Only one was relatively circumscribed o n neuroradiologic study. All were infiltrative in their histologic growth p attern and predominantly glial in appearance, being composed mainly of fibr illary, gemistocytic, or protoplasmic astroglial elements of WHO grade II t o III. Their distinguishing feature was their content of sharply delimited, neuropil-like islands of intense synaptophysin reactivity inhabited and ri mmed in rosetted fashion by cells demonstrating strong nuclear immunolabeli ng for the neuronal antigens NeuN and Hu. These cells included small, oligo dendrocyte-like ("neurocytic") elements as well as larger, more pleomorphic forms. Two cases contained, in addition, well-differentiated neurons of me dium to ganglion-cell size. Proliferative activity was observed principally within the glial compartment; two cases contained mitotic figures and exhi bited relatively elevated MIB indices (6.8% and 8.2%). One of the latter pr ogressed and proved fatal at 30 months following subtotal resection and rad iotherapy. The three other patients are alive at intervals of 14 to 83 mont hs, two tumor-free and one with extensive disease associated with the appea rance of enhancement on MRI. This glioneuronal tumor variant may pursue an unfavorable clinical course.