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Washington University Experience | NEOPLASMS (MENINGIOMA) | Brain Invasion | 5B3 Meningioma, atypical, brain invasion (Case 5) H&E 1

5B3,4 This hypercellular neoplasm consists of variably spindled and epithelioid cells with round to oval nuclei and hyperchromatic or stippled chromatin, arranged in relatively patternless sheets but also exhibiting areas of whorling and nodule formation. Five of the five atypical histological features are identified: hypercellularity, prominent (macro) nucleoli, multifocal spontaneous necrosis, small cell change, and loss of architecture ('sheeting'). Mitoses are observed at variable density that ranges up to 5 per 10/HPF in several areas.

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