Giant Mesenteric Extrauterine Leiomyoma Mimicking an Ovarian Malignancy in a Postmenopausal Woman: A Case Report

A 56-year-old postmenopausal woman presented with recurrent right-sided lower abdominal pain of approximately eight to 10 years' duration and progressive right lower abdominal swelling for five years.She had undergone five previous caesarean sections but had no history of myomectomy, hysterectomy, or ovulation-induction treatment.Computed tomography demonstrated a large, well-defined, lobulated complex right adnexal mass measuring 11.87 × 14.59 × 24.36 cm, with cystic and moderately enhancing solid components and distortion of the adjacent urinary bladder.The uterus was normal in size with no identifiable uterine mass.Ultrasonography classified the lesion as an Ovarian-Adnexal Reporting and Data System (O-RADS) category 4 complex right adnexal mass considered likely to be ovarian in origin.Serum CA-125 was 27.9 U/mL.Exploratory laparotomy was performed because of the patient's postmenopausal status, large tumour size, and complex imaging features.Intraoperatively, the uterus and ovaries were not the apparent source of the mass.Instead, a large pedunculated, partly cystic tumour was identified arising from the mesentery and abutting the caecum without involvement of the caecal wall.The mass was completely resected.Histopathological examination demonstrated a benign smooth-muscle tumour most consistent with leiomyoma.The postoperative course was uncomplicated, and the patient was discharged on postoperative day 7.At follow-up, she remained asymptomatic with a well-healed wound.This case demonstrates the diagnostic challenge posed by a large mesenteric leiomyoma presenting as an apparent ovarian mass in a postmenopausal woman.Surgical exploration and histopathological examination established the diagnosis when the anatomical origin of the mass could not be confidently determined preoperatively.