A suprasellar tumor in an 11-year-old boy is excised. It contains nests of palisading basaloid epithelium, wet keratin, and calcification, surrounded by reactive gliotic brain tissue. Immunohistochemistry shows nuclear accumulation of a signaling protein in the epithelial nests. What is this protein?

• A Beta-catenin ✓
• B S100 protein
• C Chromogranin A
• D GFAP

Explanation

Adamantinomatous craniopharyngioma occurs predominantly in children, shows palisaded squamous epithelium, stellate reticulum, wet keratin, and calcification, and is driven by activating CTNNB1 mutations producing nuclear beta-catenin accumulation. Papillary craniopharyngioma, by contrast, occurs in adults, lacks wet keratin and calcification, and harbors BRAF V600E mutation instead. Chromogranin marks neuroendocrine cells such as pituitary adenomas, S100 and GFAP mark supporting cells, and none are drivers of this tumor.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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