TABLE 1.

Theories proposed for the etiology of endometriosis.

Theory	Mechanism proposed
Retrograde menstruation theory	Retrograde menstruation permits implantation of endometrial glands and stroma into the peritoneal cavity (13)
Coelomic metaplasia theory	Endometriosis can develop in all celomic wall derivatives because of a metaplastic phenomenon (27)
Hematogenous/lymphatic spread theory	Dissemination of endometrial cells takes place by lymphatic or hematogenous vessels (35)
Stem cell recruitment theory	Endometrial and/or hematopoietic stem cells could differentiate into endometriotic tissue at different anatomical sites (37)
Embryogenetic theory	Persistence of residual embryonic cells of Wolffian or Müllerian ducts may develop into endometriotic lesions in response to estrogen (17)

The most relevant references are indicated.