CDKN2A and meningioma: Anaplastic (malignant) meningiomas are defined as meningiomas, which show (1) markedly elevated mitotic activity (20 or more mitoses in 10 consecutive high-power fields each of 0.16 mm2, at least 12.5 per 1 mm2); (2) frank malignant cytology, resembling carcinoma, melanoma, or sarcoma; (3) harbor TERT (telomerase reverse transcriptase [1]) promoter mutation; and (4) harbor CDKN2A (cyclin-dependent kinase inhibitor [1]) and/or CDKN2B homozygous deletion [1].