Dedifferentiated liposarcoma is a liposarcoma that contains a well-differentiated liposarcoma component juxtaposed to areas of high-grade non-lipogenic sarcoma and was believed to occur from well-differentiated liposarcoma after several years. Dedifferentiated liposarcoma most commonly occurs in the retroperitoneum, while an intraperitoneal location is extremely rare, only seven cases have been reported in literature. Many pathologists recognize that a large number of intra-abdominal poorly differentiated sarcomas are dedifferentiated liposarcomas. We present the case of a 73 years old patient known with multiple cardiovascular comorbidities, stroke sequelae and a large abdominal mass evolving for 3 years. He was referred to our clinic for abdominal pain and bowel disorders. Instead of all clinical and imagistic aspects suggested a gastrointestinal stromal tumour, the histological exam revealed the diagnosis of a dedifferentiated liposarcoma.