Using qRT-PCR and immunohistochemistry (IHC), we analyzed the expression, localization and correlation of CDH1 and TWIST1, CDH1 and SNAIL, CDH1 and SLUG, and TWIST1 and MYC in more than 100 ectopic and eutopic endometrial tissues from the proliferative and secretory endometrium of women with endometriosis and in matched tissue samples from the same patients. The gene discussed is TWIST1; the disease is endometriosis.