A 6-year-old girl presents with raised intracranial pressure. MRI shows a mass filling the fourth ventricle. Histology shows a moderately cellular glial tumor with ependymal cells arranged around blood vessels in a nuclear-free zone. What is this characteristic structure called?

• A Perivascular pseudorosette ✓
• B Homer Wright rosette
• C Flexner-Wintersteiner rosette
• D Ependymal rosette around a true lumen

Explanation

Ependymomas characteristically show perivascular pseudorosettes: tumor cells arranged radially around vessels with an anuclear zone formed by fibrillary cell processes. True ependymal rosettes, with a central lumen resembling a central canal, are less common. Homer Wright rosettes lack a lumen and indicate neuroblastic differentiation, seen in medulloblastoma. Flexner-Wintersteiner rosettes contain a central lumen with retinal differentiation and are seen in retinoblastoma. Ependymoma is the third most common posterior fossa tumor in children.

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.