Endometrioma involving the perianal tissues: Report of a case

Summary and Conclusions Endometriosis may involve the uterine cavity (internal) or ectopic areas outside the uterus (external). The usual sites of external endometriosis are within the pelvic cavity. They include the ovary, peritoneal surface of the uterus, uterosacral ligaments, cul de sac, peritoneum, uterovesical peritoneum, the rectovaginal septum, the rectum, all parts of the colon, the appendix, and the ileum. Less common locations for ectopic endometriosis include the umbilicus, abdominal wall scars, the vulva, and the perineum. Endometriosis involving the perianal tissues is rare, and when found it is ussually located in the perineum at the site of previous episiotomy scars. The generally accepted explanation for the pathogenesis of external endometriosis is a combination of Sampson's⁶ retrograde-flow theory and the theory of metaplasia expounded by Gruenwald.³ A case of endometriosis involving the perianal tissues in a 29-year-old woman has been presented. The diagnosis was entertained prior to surgery because of the relationship of the symptoms to the patient's menstrual cycle, but confirmation of the diagnosis depended upon pathologic study of the tumor mass, which showed endometrial glands and stroma typical of endometriosis. Read at the meeting of the Pennsylvania Society of Colon and Rectal Surgery in conjunction with the Sectional Meeting of the Pennsylvania State Medical Society, Lancaster, Pennsylvania, November 18, 1970.