Liesegang rings and endometriosis.

Liesegang rings (LRs) are acellular, ringlike structures that may from within and around inflamed or necrotic tissue. LRs are most commonly found within the kidneys, synovium, and eyelid and in association with pelvic inflammatory disease and other infectious processes. LRs are only rarely found within the female genital tract, usually within endometriotic cysts or around areas of chronic inflammation. Three additional patients with LRs associated with endometriosis are described. In one of them, LRs occurred at the edge of an endometriotic cyst adjacent to a well-differentiated endometrioid adenocarcinoma of the ovary. All cases were characterized by the presence of multiple eosinophilic, sharply demarcated ringlike structures that were highlighted by the periodic acid-Schiff method. LRs within the female genital tract, which appear to be closely related to endometriosis, should be distinguished from both benign or malignant processes.