Evidence shows that mutations in ARID1A, PIK3CA and phosphatase and tensin homolog (PTEN) play a role in the transformation of endometriosis to OCCC.39,40 Such mutations and loss of protein expression are usually found in the arising group but not in the coexisting group.41 However, the clinicopathological characteristics are not found to be different between the two groups and there may also be no difference in survival.15 Nevertheless, literature is scarce and further investigations comparing the arising and coexisting group are needed. The gene discussed is ARID1A; the disease is endometriosis.