A 6-year-old girl has morning headaches and vomiting for 3 weeks, followed by truncal ataxia and a head tilt. Fundoscopy shows papilledema. MRI reveals a midline cerebellar vermian mass compressing the fourth ventricle with obstructive hydrocephalus. Histology shows small round blue cells forming Homer Wright rosettes. What is the diagnosis?
- A Juvenile pilocytic astrocytoma
- B Ependymoma
- C Medulloblastoma ✓
- D Craniopharyngioma
Correct answer: C. Medulloblastoma
Explanation
A midline cerebellar vermis mass in a child with raised intracranial pressure, histologically composed of small round blue cells with Homer Wright rosettes, is medulloblastoma. It characteristically fills the fourth ventricle, causing hydrocephalus, and can seed the CSF pathways. Juvenile pilocytic astrocytoma is usually cystic with an enhancing mural nodule, often off-midline, and shows Rosenthal fibers. Ependymoma arises from the ventricular lining rather than the vermis, and craniopharyngioma is suprasellar with calcification, not cerebellar.
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.