Histology
Typical endometriotic lesions show histopathologic features similar to endometrium, namely endometrial stroma, endometrial epithelium, and glands that respond to hormonal stimuli. Older lesions may display no glands but hemosiderindeposits (see photomicrograph on right) as residual.
Immunohistochemistry has been found to be useful in diagnosing endometriosis as stromal cells have a peculiar surface antigen, CD10, thus allowing the pathologist go straight to a staining area and hence confirm the presence of stromal cells and sometimes glandular tissue is thus identified that was missed on routine H&E staining.