Liposarcoma is a tumor that arises from fat tissue. This tumor often occurs in the thigh, legs, behind the knee, or in the abdomen, but it can be found in other parts of the body, in the retroperitoneum; and, less often, in the head and neck area. Their primary occurrence in the skin is rare. Because a liposarcoma may grow into surrounding tissues or organs, it is considered a malignant tumor. The World Health Organization classification of soft tissue tumors recognizes 5 types of liposarcomas: Well differentiated, which includes the adipocytic, sclerosing, and inflammatory subtypes; dedifferentiated; myxoid; round cell; and pleomorphic. Most patients with liposarcoma have no symptoms until the tumor is large and invades the neighboring organs or tissues, causing tenderness, pain, or functional problems. Although surgical removal of the tumor is the curative treatment, some patients may benefit from chemotherapy and radiation.

Most patients with liposarcoma have no symptoms until the tumor is large and impinges on neighboring structures, causing tenderness, pain, or functional disturbances. In the retroperitoneal area, where liposarcoma is detected at a late stage, the tumor may grow to a substantial size, weighing several pounds at the time of diagnosis. In general, liposarcoma grows silently, and the patient's estimation of the clinical duration is often unreliable. The patient eventually becomes aware of a swelling or a mass and reports this finding to the physician.

Patients may report the following:

• Associated episode of trauma to the region containing the mass
• Painful swelling (occurs in one third of cases for as long as 6 mo)
• Decreased function (ie, range of motion)
• Numbness
• Enlargement of varicose veins
• Fatigue
• Abdominal pain
• Weight loss
• Nausea
• Vomiting