A recent large-scale molecular genetic analysis of uterine carcinosarcomas by the Cancer Genome Atlas 148 revealed extensive copy-number alterations and highly recurrent somatic mutations, most frequently in TP53, PTEN, PIK3CA, PPP2R1A, FBXW7, and KRAS. The similarity in mutational profile to uterine endometrioid and serous carcinomas provides genomic support for the categorization of carcinosarcomas as a subset of uterine carcinomas. This evidence concerns the gene PPP2R1A and serous adenocarcinoma.