ARID1A (AT-rich interactive domain 1A) mutations and consequent loss of BAF250a (BRG-associated factor 250a) protein expression were particularly identified in EAOC, and in the contiguous atypical endometriotic lesions, but not in distinct endometrioid lesions far from the carcinoma, suggesting such phenomenon as a possible early event in the malignant transformation of endometriosis [19, 20]. This evidence concerns the gene ARID1A and endometriosis.