A 35-year-old woman presents with progressive hydrocephalus. MRI shows an intraventricular mass arising from the fourth ventricle. Histology shows tumor cells arranged around blood vessels forming perivascular pseudorosettes with GFAP-positive processes radiating toward the vessel wall. True ependymal rosettes (true lumina) are also seen. What is the diagnosis?

• A Medulloblastoma
• B Central neurocytoma
• C Ependymoma ✓
• D Choroid plexus papilloma

Explanation

Ependymomas arise from ependymal lining of ventricles, most commonly the fourth ventricle in children and young adults. The hallmark histological feature is perivascular pseudorosettes: tumor cells arranged around blood vessels with GFAP-positive processes radiating toward the vessel wall. True ependymal rosettes (true lumina) are less common but diagnostic. Medulloblastoma shows Homer Wright rosettes. Central neurocytoma shows uniform round cells with 'fried egg' appearance. Choroid plexus papilloma shows papillary architecture.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.