A 7-year-old boy presents with morning headaches, vomiting, and truncal ataxia. MRI shows a 4 cm midline posterior fossa mass in the vermis, hypointense on T1, hyperintense on T2, with homogeneous enhancement. CSF cytology is positive. What is the most likely diagnosis?
- A Pilocytic astrocytoma
- B Ependymoma
- C Medulloblastoma ✓
- D Hemangioblastoma
Correct answer: C. Medulloblastoma
Explanation
Medulloblastoma is the most common malignant pediatric brain tumor, typically arising in the cerebellar vermis in children. It presents with signs of raised ICP and cerebellar dysfunction. MRI shows a midline enhancing mass. It is a primitive neuroectodermal tumor (PNET) with a propensity for CSF dissemination, explaining positive CSF cytology. Pilocytic astrocytoma is typically cystic with a mural nodule. Ependymoma often extends through the foramen of Luschka.
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.