Endometriotic lesions commonly carry multiple somatic mutations; atypical endometriosis and co-existing tumors share nearly all of the somatic mutations, such as driver mutations in ARID1A, PIK3CA and high expression of MET and HNF1β, and it is thought that those above mutations occurred early in the malignant transformation of the OCCC (Figure 3 & 4, Table 1) . Here, PIK3CA is linked to endometriosis.