A 6-year-old boy presents with progressive hydrocephalus. MRI reveals an enhancing intraventricular mass in the fourth ventricle. Histology shows tumor cells arranged around blood vessels forming perivascular pseudorosettes. True rosettes (Flexner-Wintersteiner) are absent. What is the diagnosis?

• A Medulloblastoma
• B Subependymoma
• C Central neurocytoma
• D Ependymoma ✓

Explanation

This describes ependymoma, which classically arises in the fourth ventricle in children. The hallmark histological feature is perivascular pseudorosettes, where tumor cells radiate around blood vessels with their processes pointing toward the vessel wall. True ependymal rosettes (around a central lumen) are rare. Medulloblastoma shows Homer Wright rosettes. Central neurocytoma occurs in the lateral ventricles and shows a 'fried egg' appearance. Subependymoma is benign and non-enhancing.

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.