However, it remains controversial at which stage of pathogenesis ARID1A mutations occur in endometriosis, i.e., if they are limited to atypical endometriosis or if they already occur in a low-frequent manner in non-atypical endometriosis or at the early transition stage from non-atypical to atypical endometriosis. This evidence concerns the gene ARID1A and endometriosis.