Pleomorphic leiomyosarcoma of colonic mesentery: an unusual cause of lower GI bleed - case report and literature review

Abstract

Mesenteric masses are infrequent lesions ranging from benign cyst to aggressive malignancies and often present as diagnostic and therapeutic challenge. The mesentery is a frequent recipient of metastasis from the gastrointestinal tract, pancreas, and biliary cancers. Primary mesenteric tumours are relatively rare, mostly mesenchymal in origin and benign in nature. Examples include gastrointestinal stromal tumours and smooth muscle tumours. Pleomorphic leiomyosarcoma of mesocolon is extremely rare with a reported incidence of 1:350,000. So accurate preoperative diagnosis of mesenteric soft tissue tumours is generally difficult. It accounts for less than 1% of the malignant tumours found in colon. Leiomyosarcoma is a malignant tumour arising from smooth cell lineage. These tumours occur most commonly in middle aged individuals. We describe a case of pleomorphic leiomyosarcoma arising from the colonic mesentery in a 27-year-old male patient, with massive lower gastrointestinal bleed (LGI bleed) causing drop in haemoglobin level from 9 mg/dl to 6 mg/dl. Ultrasonography and CECT abdomen suggestive of (17.5×11.6×10.6) cm mass in left side upper abdomen in splenic hilar region. Left hemicolectomy with excision of mass with splenectomy and distal pancreatectomy done. The diagnosis was based on histopathological evaluation using immunohistochemistry (IHC). Histopathological report suggestive of pleomorphic leiomyosarcoma with SMA and vimentin positivity on immunohistochemistry but CD 34 and CD 117 were negative, differentiating it from GIST.