A 5-year-old boy presents with morning headaches and vomiting. MRI shows a midline cerebellar vermian mass causing obstructive hydrocephalus, with nodular enhancement along the lumbosacral leptomeninges. Biopsy shows small round blue cells with Homer Wright rosettes. Which molecular subgroup of this tumor carries the worst prognosis?
- A Group 3 medulloblastoma with MYC amplification ✓
- B SHH-activated medulloblastoma
- C WNT-activated medulloblastoma
- D Group 4 medulloblastoma
Correct answer: A. Group 3 medulloblastoma with MYC amplification
Explanation
Medulloblastoma is divided into four molecular groups. Group 3 tumors show MYC amplification, frequent metastasis at presentation, and the worst overall survival. The WNT group has the best prognosis with CTNNB1 mutations, while the SHH group shows PTCH1/SUFU alterations and a desmoplastic/nodular histology in infants and adults. Group 4 is the commonest group with an intermediate prognosis. Leptomeningeal seeding via CSF is typical of all groups but is most frequent in Group 3.
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.