An 8-year-old boy presents with morning headache, truncal ataxia, and papilloedema. MRI shows a homogeneous enhancing midline posterior fossa mass arising from the vermis with hydrocephalus. Leptomeningeal drop metastases are noted. Which tumor is most likely?
- A Pilocytic astrocytoma
- B Ependymoma
- C Medulloblastoma ✓
- D Hemangioblastoma
Correct answer: C. Medulloblastoma
Explanation
Medulloblastoma is the most common malignant brain tumor of childhood, typically arising from the cerebellar vermis in children (midline) or cerebellar hemispheres in young adults. It is a small round blue cell tumor, WHO grade 4, with a propensity for CSF dissemination (drop metastases). Pilocytic astrocytoma is cystic with a mural nodule. Ependymoma arises from the fourth ventricle and can extend through foramina. Hemangioblastoma is associated with VHL and is cystic with a mural nodule (WHO CNS Tumours, 5th ed.).
Reference: WHO Classification of Tumours of the CNS, 5th ed.
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Written and medically reviewed by the StethoPrep medical team.