The role of the lymphatic system in endometriosis: a comprehensive review of the literature.

Endometriosis is a benign gynecological disorder characterized by the presence of tissue resembling the endometrium in locations outside the uterus. The pathogenesis of endometriosis is still unknown; however, it is believed that the lymphatic system plays major roles in the development and progression of the disease. The lymphatic dissemination theory has been proposed to explain the presence of endometrial and/or endometriotic tissue in lymphatic vessels, lymph nodes, and rare sites, as well as high reoccurrence rates following treatment. Despite the importance of the lymphatic system in many aspects of endometriosis, there has been no previous thorough scientific update on its role in the disease. A review of scientific literature on the lymphatic system, lymphangiogenesis, and immunological changes associated with endometriosis was conducted. Lymphangiogenic potential is disturbed and lymphatic vessel density increased in the eutopic endometrium of women with endometriosis, likely promoting the entry of endometrial tissues into the lymphatic circulation. Endometriotic lesions and endometrial-like cells are present in uterine-draining nodes and various other pelvic lymph nodes. Immune responses are impaired in uterine-draining nodes, likely favoring the survival of endometrial cells and lesion establishment. In addition, lymphangiogenesis in endometriotic lesions may contribute to lesion growth and persistence, and promote the spread of endometrial cells to draining lymph nodes. The evidence reviewed in this paper supports the theory of lymphatic dissemination of endometriosis and highlights the roles of the lymphatic system in the pathogenesis and persistence of endometriosis. Understanding these roles is crucial for establishment of novel therapeutic approaches.