A 4-year-old boy presents with morning headaches and vomiting. MRI shows a midline cerebellar vermian mass compressing the fourth ventricle. Biopsy shows small round blue cells with Homer Wright rosettes and areas of nodularity. Which molecular subgroup of this tumor carries the best prognosis?

• A WNT-activated ✓
• B SHH-activated
• C Group 3 (MYC-amplified)
• D Group 4

Explanation

Medulloblastoma is now classified into four molecular groups. WNT-activated tumors carry CTNNB1 mutations and have an excellent prognosis with survival exceeding 90 percent, allowing treatment de-escalation trials. SHH-activated tumors are intermediate, common in infants and adults. Group 3 with MYC amplification has the worst prognosis, which is the fact that kills option C as an answer.

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.