Firstly, it may explain the observation of ARID1A expression in non-atypical endometriosis made by several groups [101,104,106]; loss of ARID1A expression may be an early molecular event in these cases that might increase the overall risk of developing endometriosis-associated cancer, but in itself is not sufficient to initiate cancerogenesis. The gene discussed is ARID1A; the disease is endometriosis.