20 or more mitotic figures in 10 consecutive HPF of each 0.16 mm2 (at least 12.5/mm2)ORFrank anaplasia (sarcoma-, carcinoma, or melanoma-like appearance)ORTERT promoter mutationORHomozygous deletion of CDKN2A and/or CDKN2B. The gene discussed is CDKN2B; the disease is sarcoma.