First reported case in Brazil of intraventricular pilocytic astrocytoma in an adult patient with literature review.

BACKGROUND

Pilocytic astrocytomas (PAs) are central nervous system tumors that predominantly occur during the first two decades of life and typically arise in the cerebellum, optic pathways, hypothalamus, or brainstem. Intraventricular PAs are extremely uncommon, accounting for less than 4% of all cases, and adult presentations are particularly rare. We report the first documented case of an intraventricular PA in an adult patient in Brazil and highlight its clinical and therapeutic relevance.

CASE REPORT: A 32-year-old Brazilian woman presented with a secondary epileptic seizure. Magnetic resonance imaging revealed an expansive lesion in the left lateral ventricle. The tumor was surgically resected, and histopathological examination showed a biphasic neoplasm with eosinophilic granular bodies and microcystic areas. Immunohistochemical analysis demonstrated positivity for glial fibrillary acidic protein (GFAP) and oligodendrocyte transcription factor 2 (OLIG2), with no expression of mutant isocitrate dehydrogenase 1 protein (IDH1 R132H). Expression of 5'-methylthioadenosine phosphorylase (MTAP), alpha-thalassemia/mental retardation syndrome X-linked (ATRX), and the tumor suppressor protein p16 (INK4a) was retained. The Ki-67 (MIB-1) proliferation index was low, at approximately 1%, consistent with a WHO Grade 1 glioma.

CONCLUSIONS

This case illustrates a rare intraventricular PA in an adult, confirmed through clinical, radiological, and histopathological integration. It emphasizes the importance of including PA in the differential diagnosis of intraventricular tumors in adults and may contribute to guiding recognition and management of rare ventricular tumors in this population.