Abstract: Endometriosis is one of the most enigmatic diseases in women. Extensive research has been carried out in the past since endometriosis has a significant impact in women's life. However, the pathogenesis of endometriosis remains unclear. In this review, we briefly summarized four main theories associated with the cell origin of endometriosis including retrograde menstruation, coelomic metaplasia from ovarian or peritoneal surface, embryonic rests from Müllerian tissue, and endometrioid tissue induction by hematopoietic stem cells. In addition, we have added our recently proposed theory of tubal origin of ovarian endometriosis based on our clinicopathological observations and recent experimental results. It would be interesting to know if the tubal contribution in the genesis of ovarian endometriosis can be truly accepted in future after additional in depth studies in various clinical, pathological, and molecular levels
