Primary Mesenteric Leiomyosarcoma Presenting as a Migrating Abdominal Mass: A Rare Case Report and Literature Review

Abstract

Aim: The aim of this case report is to present and critically analyze a rare instance of primary mesenteric leiomyosarcoma, an exceptionally uncommon malignant tumour arising from smooth-muscle of the mesentery. This case highlights the unusual presentation of the tumour as a migrating abdominal mass, a feature seldom described in the literature. Presentation of Case: A 74‑year‑old male presented with a painless, mobile abdominal swelling. Contrast‑enhanced computed tomography (CECT) revealed a heterogeneously enhancing soft-tissue lesion in the anterior pararenal space. Exploratory laparotomy revealed a 10.5 × 10.0 cm mass in the jejunal mesentery, 80 cm from the duodenojejunal flexure. The lesion was resected en bloc with a 50 cm segment of jejunum, followed by end‑to‑end anastomosis. Histopathology and immunohistochemistry confirmed leiomyosarcoma (SMA+, H‑Caldesmon+, CD117−). A small hepatic nodule showed metastatic deposits. Postoperative PET‑CT demonstrated no residual disease and adjuvant chemotherapy was initiated. Discussion: Primary mesenteric leiomyosarcoma is an exceedingly uncommon tumour arising from smooth‑muscle elements of the mesenteric vessels. Because of the expansile nature of the mesentery, tumours often remain clinically silent until large, resulting in delayed diagnosis. Imaging, histopathology, and immunohistochemistry are essential for diagnosis, and surgical excision with negative margins remains the cornerstone of treatment. Adjuvant therapy may improve control in high‑risk cases. Conclusion: Mesenteric leiomyosarcoma poses a diagnostic and therapeutic challenge due to its rarity and aggressive behaviour. Early recognition, complete resection, and long‑term surveillance are crucial for improving patient outcomes. In the present case, the tumour measured 10.5 × 10.0 cm and displayed metastatic spread to the liver. Despite these adverse prognostic features, the patient achieved disease-free survival at one year following R0 resection and adjuvant doxorubicin-based chemotherapy.