Diagnosis of leiomyosarcoma of colon

Leiomyosarcomas of colon are rare tumors accounting for less than 1% of cases which are often misdiagnosed and confused with gastrointestinal stromal tumor (GIST). We report a case of 54-year-old male presenting with abdominal pain with computer tomography (CT) showing a retroperitoneal mass. He underwent laparotomy and surgical excision of mass was done. On pathological examination, microscopy was suggestive of GIST, but immunohistochemistry was positive for desmin and ultimately this case was diagnosed as leiomyosarcoma.