A rare case report of small bowel leiomyosarcoma with literature review.

Small bowel leiomyosarcoma (LMS) is a rare and aggressive malignancy that often presents with nonspecific abdominal symptoms, leading to delayed diagnosis and poor prognosis. We report the case of a 73-year-old male with an eight-month history of abdominal pain, constipation and anemia. Computed tomography revealed partial small bowel obstruction caused by a mass, and exploratory laparotomy identified an ulcerated lesion involving the small bowel and mesentery. The mass was completely resected with primary anastomosis. Histopathological examination confirmed a high-grade LMS with a high mitotic index, positive for smooth muscle actin and desmin, and negative for CD34, S100, and CD117. Notably, weak DOG1 positivity was observed, a rare finding that may complicate distinction from gastrointestinal stromal tumours. This case highlights the diagnostic challenges of small bowel LMS, the central role of surgical resection in management, and the need for careful pathological evaluation to avoid misclassification and guide prognosis.