Liposarcomas develop in fatty cells and tissue. Because they are malignant, they can metastasize to other parts of the body. Liposarcomas are usually found in the thigh, abdomen, or around the knees. Symptoms of liposarcoma include a growing lump, swelling and/or numbness around the lump, bloody or black stool, bloody vomit, and pain or cramping in the abdomen. Liposarcomas can be divided into four categories: well-differentiated, myxoid, pleomorphic, and dedifferentiated. Well-differentiated liposarcomas are the most common and grow slowly. Myxoid liposarcomas are more serious, and can grow more quickly. Pleomorphic liposarcomas are the rarest type, and can progress quickly. Dedifferentiated liposarcomas develop when low-grade tumors change and start producing high-grade cells. Liposarcomas are usually treated using surgery to remove the lump, chemotherapy, and radiation. Biopsies can also be used to diagnose liposarcomas.