An unexpected diagnosis of primary omental endometrial stromal sarcoma in a patient with acute right abdominal pain: A case report and review of literature.

INTRODUCTION: Extrauterine Endometrial Stromal Sarcoma (EESS) is an extremely rare mesenchymal tumour that simulates other pathologies, and therefore poses a diagnostic challenge. This report outlines a case of EESS arising from the greater omentum mimicking a colonic tumour, with review of literature.

PRESENTATION OF CASE: A 47-year-old woman, with history of hysterectomy for menorrhagia and hormone replacement therapy (HRT), presented with right sided abdominal pain and localized peritonism. On exploratory laparoscopy an omental tumour, suspected to arise from the transverse colon was identified and biopsied. The histological features suggested an EESS. Colonoscopy ruled out colonic lesion. A laparoscopic tumour resection and bilateral salpingo-oophorectomy (BSO) was performed. Immunohistochemistry confirmed the diagnosis. No additional lesions or associated endometriosis were found. Resection was followed by adjuvant medroxyprogesterone-acetate therapy.

DISCUSSION: We reviewed 20 cases of EESS originating from extragenital abdominopelvic organs reported since 1990. Acute presentation is rare, as well as upper abdominal occurrence. Isolated omental involvement was previously reported in only one case. Endometriosis is a risk factor for development of EESS and history and/or histological evidence for endometriosis is usually present. HRT is another acknowledged risk factor, mostly on the background of endometriosis. To our knowledge, this is the only report of EESS occurring in a woman on HRT treatment without background of endometriosis.

CONCLUSION: EESS can occur without endometriosis and HRT may be an aetiological factor. The condition can mimic a chronic or acute abdominal pathology and laparoscopic core biopsy is the best way to achieve a diagnosis and formulate management.