Endometriosis and endometriotic cysts: Thoughts on pathogenesis, considering clinicopathologic, histopathologic and molecular biologic studies

Endometriosis is thought to arise by either metaplastic change of coelomic cells, or via implantation of menstrual tissue in ectopic sites, as a result of transtubal or intravascular migration. Endometriosis has a biochemical phenotype distinct from that of native uterine endometrium and from adenomyosis. It may occur either in the form of solid or as cystic lesions; the latter occurring most frequently in the ovaries. The theories on pathogenesis of cystic and solid endometriosis are discussed, with a brief review of supporting data, including clinicopathologic, histologic, and molecular biology studies in the current literature.