Liposarcomas are malignant soft tissue neoplasms usually located in the retroperitoneum, head, neck and extremities. Although secondary invasion of the gastrointestinal tract by retroperitoneal sarcomas is frequent, primary involvement is uncommon. We report a young patient with Crohn's disease in remission presenting with intussusception of the colon due to a primary liposarcoma of the sigmoid. Emergency resection confirmed the diagnosis. The patient remains in remission after five years. This represents the youngest diagnosis of liposarcoma to date and the first occurring in the sigmoid. We also highlight the concomitant diagnosis of Crohn´s disease.