A meningioma resected from a 55-year-old woman shows a benign meningothelial morphology with fewer than 4 mitoses per 10 high-power fields, but tumor is seen infiltrating into the underlying brain parenchyma. According to the WHO CNS classification, what grade should be assigned?

• A Grade 1, because mitotic count is low
• B Grade 3, because brain invasion defines anaplastic meningioma
• C Grade 2, because brain invasion upgrades any meningioma to at least grade 2 ✓
• D Grading cannot be assigned without Ki-67 index

Explanation

Brain invasion by a meningioma mandates assignment of at least WHO grade 2 irrespective of other histological features, because it predicts recurrence. Grade 2 also applies with 4 to 19 mitoses per 10 HPF or specified histological patterns such as chordoid and clear cell. Grade 3 requires 20 or more mitoses per 10 HPF or frank anaplasia resembling sarcoma or carcinoma. Ki-67 is prognostic information but not required for grading.

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.