H2BC21 and endometrial serous adenocarcinoma: Further to mutations in cancer genes already observed in uterine and ovarian CS such as TP53, PIK3CA, PPP2R1A, KRAS, PTEN, CHD4, and BCOR, this study identified an excess of mutations in genes encoding histone H2A and H2B, demonstrating a stable transgenic expression of H2A and H2B in a uterine serous carcinoma cell line.