Endometriosis (EM) is one of the most common diseases which severely affect the health and reproductive function of women of childbearing age. There are fundamental abnormal changes within the eutopic endometrium of women with endometriosis compared to normal endometrium of women without endometriosis. Eutopic endometrium shows enhanced ability of proliferation, implantation and angiogenesis, and greater probability of escaping the unfavorable conditions of the ectopic environment. Therefore, the character of eutopic endometrium determines the fate of the backward-flowing endometrial tissue – to live or to die. The abnormal endometrial tissue in EM patients flows backward to the pelvic cavity, completing a 3-step procedure of pathogenesis (attachment-aggression-angiogenesis), and ultimately develops into EM. Abnormal eutopic endometrium may also play important roles in endometriosis-associated infertility. This recognition regarding the pathogenesis of endometriosis ultimately will help to discover new methods for diagnosis and treatment. Endometrial markers for micro-invasive diagnosis and direct treatment of eutopic endometrium as the origin of the disease should be further investigated.

Keywords: Infertility, Female - etiology, Epithelium - pathology, Endometrium - pathology, Endometriosis - therapy, Cell Adhesion, Peritoneum - pathology