S2958 Endometriomas as the Cause of Abdominal Wall Masses in a Woman With Cyclical Abdominal Pain

INTRODUCTION: Endometriosis is characterized by the presence of endometrial tissue outside the uterine cavity. When endometriosis forms a distinct mass, it is termed an endometrioma. Extra-pelvic endometriosis is rare, accounting for less than 12% of reported cases. Among these, one of the rarest forms is abdominal wall endometriosis. The diagnosis of abdominal wall endometriosis can be challenging, and requires a high index of suspicion. CASE DESCRIPTION/METHODS: A 48-year-old woman with a history of a locally treated left second toe melanoma and a previous cesarean section (C-section) presented for evaluation of cyclic abdominal pain of several years duration. Her discomfort was localized to the right lower quadrant associated with her menstrual period. Physical examination revealed two tender small nodules, one in the right lower quadrant and one in the midline approximately at the level of her prior C-section scar. CT imaging of the abdomen/pelvis performed at an outside institution demonstrated two nodules along the abdominal wall associated with the musculature measuring 2.2- and 1.5-cm in diameter (Images 1 and 2). Locally, a laparoscopy was normal revealing no evidence of endometriosis. Given her previous history of melanoma and to also rule out the possibility of desmoid tumor, we proceeded with an ultrasound-guided biopsy. Histopathology demonstrated fibrous tissue involved by endometriosis in the area along the prior C-section scar (Image 3). She was evaluated by gynecology and general surgery to discuss oral contraceptives, ablative therapy, or surgical resection, and decided on hormonal therapy as initial treatment. DISCUSSION: Abdominal wall endometriosis has a reported incidence of 0.03–1.5% following C-section or pelvic surgery. Symptom fluctuation with the menstrual cycle and presence of gynecologic surgical scars are important clues hinting at the diagnosis. The clinical diagnosis of abdominal wall endometrioma has been confused with abscess, lipoma, hernia, desmoid tumor, or primary and metastatic malignancies. Ultrasound, CT imaging, and MRI are useful noninvasive techniques when the diagnosis is unclear. Percutaneous biopsy can yield a definitive diagnosis. Therapies include hormonal treatment, ablative therapy, or surgical resection. This novel case highlights the importance of considering abdominal wall endometrioma in the differential diagnosis when evaluating women with an abdominal wall mass and a history of uterine surgery with cyclic abdominal pain.Figure 1.: CT scan of the abdomen and pelvis demonstrating two nodules along the abdominal wall associated with the musculature measuring 2.2- and 1.5-cm in diameter.Figure 2.: CT scan of the abdomen and pelvis demonstrating two nodules along the abdominal wall associated with the musculature measuring 2.2- and 1.5-cm in diameter.Figure 3.: Hematoxylin and eosin stain of US-guided biopsy tissue specimen from abdominal wall nodule demonstrating benign endometrial glands and stroma.