Liposarcoma is one of the most common soft tissue sarcomas found in adults,and it usually occurs in the retroperitoneum and the extremities.Here,we describe a case of dedifferentiated liposarcoma originating from a well-differentiated liposarcoma of the mesorectum that presented as a protruding mass in the rectal lumen.Hartmann’s operation with total mesorectal excision was performed and the tumor was removed radically.No management guidelines are currently available for liposarcoma of the rectum.We propose that complete surgical resection be required for the treatment of rectal liposarcoma and that a long-term detailed follow up is necessary. Liposarcoma is one of the most common soft tissue sarcomas found in adults, and it usually is in the retroperitoneum and the extremities. Here, we describe a case of dedifferentiated liposarcoma originating from a well-differentiated liposarcoma of the mesorectum that presented as a protruding mass in the rectal lumen. Hartmann’s operation with total mesorectal excision was performed and the tumor was removed radically. Management protocol are currently available for liposarcoma of the rectum. We propose that complete surgical resection be required for the treatment of rectal liposarcoma and that a long -term detailed follow up is necessary.