Atypical neuronal-glial tumors of cerebral hemispheres in adults with PNET-like component: clinicopathological...

We investigated 5 cases with brain tumors composed ofneuronal and astrocytic differentiated tumor cells occurring in the cerebral hemispheres of adults. Patients ranged from 33 - 69 years of age, 3 females and 2 males. Radiologically, contrast enhancement was demonstrated in these tumors. All tumors were surgically resected following radiotherapy and chemotherapy. Four patients have been free of recurrence for 2-5 years. One recurred 15 years after the operation. Histologically, tumor cells were mainly composed of round or oval nucleate cells with scant cytoplasm and compactly arranged with neurocytic features. Immunohistochemically, some tumor cells were immunoreactive for synaptophysin, neurofilament, beta-tubulin, chromogranin A, GFAP and vimentin. There were little immunoreactive cells for myelin basic protein and epithelial membrane antigen. Ultrastructurally, tumor cells were variably differentiated as follows: undifferentiated cells having prominent nuclei and scanty cytoplasm with inconspicuous organelles; neuronal cells consisting of neurosecretory granules or vesicles and abortive synapses, and astrocytic cells with cytoplasmic intermediate filaments. The Ki-67 labeling index ranged from 4.5 - 9.8%. Allelic loss of chromosome Ip occurred in 2 cases (50%) and allelic loss of chromosome 19q occurred in 2 cases (50%) of 4 informative cases. These tumors were characterized as neuronal and astrocytic differentiated tumors with primitive PNET-like component. However, there was little oligodendrocytic or ependymal differentiation in these tumors.