Anglesio et al demonstrated the presence of somatic mutation events in 79% of 24 cases, with 26% of all cases screened harbouring statistically significant somatic mutations in known cancer driver genes such as KRAS, PIK3CA, ARID1A, and PPP2R1A. In the analysis of a smaller subset of samples, mutations in KRAS found to be present in the epithelial component of endometriosis lesions were absent in the stroma. Here, ARID1A is linked to endometriosis.