A 45-year-old man presents with new-onset seizures. MRI shows a cortical-based mass with heterogeneous signal. Histology reveals glial neoplasm with a dual neuronal-glial differentiation, Rosenthal fibers absent, eosinophilic granular bodies present, and BRAF V600E mutation. According to WHO 2021 CNS tumor classification, the diagnosis is:
- A Ganglioglioma, WHO grade 1
- B Pleomorphic xanthoastrocytoma (PXA), WHO grade 2 ✓
- C Diffuse astrocytoma, IDH-mutant, WHO grade 2
- D Anaplastic astrocytoma, IDH-mutant, WHO grade 3
Explanation
Pleomorphic xanthoastrocytoma (PXA) is characterized by: cortical location, frequent seizures presentation, BRAF V600E mutation (~70%), eosinophilic granular bodies, dense reticulin network, and marked nuclear pleomorphism without IDH mutation. The WHO 2021 5th edition classification retains PXA as WHO grade 2 (or grade 3 if mitoses ≥5/10 HPF). BRAF V600E is its molecular hallmark and is therapeutically targetable with vemurafenib/dabrafenib. Ganglioglioma also has BRAF V600E but shows both neoplastic neurons and glial cells. IDH-mutant astrocytomas are diffusely infiltrating and lack discrete cortical borders.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.