Congenital glioneuronal tumor with neuropil-like islands.

The glioneuronal tumor with neuropil-islands is considered a rare variant of an astrocytoma. Congenital cases of glioneuronal tumor with neuropil-islands, which typically arise in adults, have not been reported to our knowledge. We report an autopsy case of an in-utero demise of a 38-week-gestation female fetus in a 29-year-old female. At autopsy, a previously detected supratentorial tectal mass (by fetal MRI) was identified. Histology showed a biphasic neoplasm marked by island of gray matter-like parenchyma rimmed by mature-appearing neuronal cells intermixed with variably cellular areas resembling a low grade astrocytoma. Focally, the tumor was noted to involve the overlying meninges. The neuronal cell components were highlighted with synaptophysin and neuN antibodies and the glioma areas stained with glial fibrillary acidic protein antibody. The tumor did not stain with isocitrate dehydrogenase 1 (R132H) antibody and had a low Ki-67 labeling index (1.4%), in keeping with a low grade tumor. The pathologic findings were interpreted as representing a low grade glioneuronal tumor with neuropil-like islands. There have been few reports of this tumor arising in children, with most of those developing in the spinal cord. To our knowledge, this is the first reported congenital case of this tumor described in the literature.