An endometrioma is a well-circumscribed mass of endometrial tissue. The diagnosis of an abdominal wall endometrioma (AWE) in patients with no history of endometriosis is difficult as AWE can be confused with other benign lesions such as suture granuloma neuroma lymphadenopathy hernia hematoma or with any neoplasm. We retrospectively reviewed the charts of 12 patients treated in our clinic for a histopathologically proven AWE between 1998 and 2004. Their characteristics are shown in. The main presenting symptom was a mass 6 (50%) of which were associated with cyclic tenderness. In 11 patients (92%) who had undergone previous surgical procedures the AWE was located near the incision site and none of these patients had a history of pelvic endometriosis. The preoperative ultrasonographic (n=4) and computed tomographic (n=1) scans performed showed solid lobulated masses in the subcutaneous tissue but those were suggestive of endometrioma in only 4 patients (33%). A recurrent inguinal hernia sac was diagnosed in the fifth patient. Fine-needle biopsy was performed in 1 patient but the result was nondiagnostic. Thus an endometrioma was accurately diagnosed preoperatively in only 33% of the patients. (excerpt)