Although not previously reported in osteosarcomas, mutations in KMT2B/MLL2, KMT2C/MLL3, or KMT2D/MLL4 that catalyze mono‐ or di‐methylation of H3K4 (Hyun et al, 2017) are frequently observed in many types of cancer (Rao & Dou, 2015; Fagan & Dingwall, 2019). The gene discussed is KMT2C; the disease is osteosarcoma.