Liposarcoma

Liposarcoma is a cancer that arises in fat cells in soft tissue, such as that inside the thigh or in the retroperitoneum. It is a rare type of cancer that bears a resemblance to fat cells when examined under a microscope. It is typically a large, bulky tumor, and tends to have multiple smaller satellites that extend beyond the main confines of the tumor. Liposarcomas, like all sarcomas, are rare.
Causes.
It's not clear what causes liposarcoma. Doctors know that liposarcoma forms when a fat cell develops errors (mutations) in its genetic code. The mutations tell the cell to multiply rapidly and to go on living when other cells would die. The accumulating abnormal cells form a mass (tumor). Several types of liposarcoma exist. Some grow slowly and the cells stay in one area of the body. Other types grow very quickly and may spread to other areas of the body.
Signs and symptoms.
Patients usually note a deep-seated mass in their soft tissue. Only when the tumor is very large do symptoms of pain or functional disturbances occur. Retroperitoneal tumors may present themselves with signs of weight loss and emaciation and abdominal pain. These tumors may also compress the kidney or ureter, leading to kidney failure.
Diagnosis.
The diagnosis is established by histologic examination of the tissue, i.e., biopsy or excision. Lipoblasts are often present; these are cells with an abundant clear multivacuolated cytoplasm and an eccentric darkly staining nucleus that is indented by the vacuoles.
Medical imaging.
Ultrasonography may not be able to distinguish a liposarcoma from a benign lipoma, and therefore, MRI is the initial imaging of choice.
Subtypes.
Several subtypes of liposarcoma exist:
Treatment.
Treatment of liposarcoma most often consists of surgical removal of the tumor and margin, occasionally radiation, and possibly chemotherapy, as well.
Prognosis.
The prognosis varies depending on the site of origin, the type of cancer cell, tumor size, depth, and proximity to lymph nodes.
Five-year survival rates vary from 56 to 100% based on histological subtype. 
Epidemiology.
Most frequent in middle-aged and older adults (age 40 and above), liposarcomas are the second-most common of all soft-tissue sarcomas, following malignant fibrous histiocytomas. Annually, 2.5 cases occur per million population.