Endometriosis in abdominal scars: a diagnostic pitfall.

Endometriosis is ectopic endometrial tissue that responds to hormonal stimulation and is found in 8 to 15 per cent of all menstruating women. Endometrioma in a surgical scar is rare and appears in 0.1 per cent of women who have undergone cesarean section; 25 per cent of these women have concomitant pelvic endometriosis. Endometrioma in a scar can present as a painful swelling on the scar that worsens during cough and effort, with the patient's complaints resembling those of a postoperative hernia occurring in a scar. It can also mimic other lesions of the abdominal wall, such as hematomas, granulomas, abscesses, and tumors. Four cases of endometriomas in a cesarean section scar are described. Two were diagnosed preoperatively as postoperative ventral hernias, and the other two presented with an abdominal wall mass causing pain and discomfort. All patients underwent surgery, and the error of their preoperative diagnosis was revealed by histology, which confirmed endometrioma. We contend that endometrioma in scarring is a diagnostic pitfall that should be considered in the differential diagnosis of postoperative ventral hernias and various abdominal wall masses.