Liposarcoma

A liposarcoma is a malignancy that develops in deep soft tissue fat.

Liposarcoma is a malignant tumor that arises from mesenchymal cells (specifically, abnormal fat cells in deep soft tissue that multiply in an unregulated manner), mainly affecting middle-age people at sites such as the thigh, gluteal region, retroperitoneum, and leg and shoulder area. Occasionally, the liposarcoma can become very large. For example, the news media has described a 30-pound liposarcoma removed from the abdomen of a 63-year-old man. Liposarcomas are one type of soft tissue sarcomas.

Liposarcoma vs. lipoma

Liposarcomas do not develop from common lipomas, which are benign tumors of fat cells.

Liposarcoma cancer cells are similar to fat cells but are thought to develop from deeper fat tissues instead of superficial fat cells beneath the skin or mucous membranes. Although liposarcomas may develop almost anywhere in the body, most develop in the abdomen and limbs. Liposarcomas are rare. They represent less than 1% of all newly diagnosed cancers. Although it is not known what triggers the development of liposarcomas, they are usually noted after trauma when a "hard lump" develops and remains but trauma or injury is not a risk factor.

Risk factors for liposarcomas may include radiation, certain family cancer syndromes (for example, neurofibromatosis, Gardner syndrome), a damaged lymph system, and/or exposure to certain chemicals (for example, vinyl chloride, dioxin).

Many liposarcoma patients do not feel sick initially so the patients seek help only late in the disease process when other symptoms arise. Symptoms depend on the location of the tumor and the extent to which it has spread in the body. Symptoms and signs that may occur later in the disease can include

• painful swelling and/or a growing lump under the skin;
• numbness;
• enlargement of varicose veins;
• fatigue and/or weakness, especially of the affected limb;
• abdominal pain, although some patients have no pain, others can experience constipation, feeling of fullness sooner when eating, and/or blood in the stool (these symptoms are more likely to develop in patients with liposarcoma the forms in the abdomen);
• chest pain;
• urinary difficulty and/or pain;
• difficulty swallowing;
• nausea;
• vomiting; and
• decreased range of motion in the limbs.

Many patients with liposarcoma will complain of a mass that they can feel. The mass can be soft and fleshy or even firm to palpation. Some doctors may initially try ultrasound, but the diagnosis usually requires standard X-rays that will help show whether or not any bony elements are involved. However, an MRI is usually obtained and may help suggest a diagnosis that must be confirmed by a biopsy. For many individuals, a chest CT is done because the chest is the most common site of metastasis (spread) of liposarcomas.

There are five subtypes of liposarcoma now recognized by WHO (World Health Organization):

• The most common type is termed well-differentiated liposarcoma (about 50% of sarcomas).
• The next type is termed myxoid (resembling mucus).
• Round cell liposarcoma is an intermediate grade of fat-cell cancers that includes round-cell variants and is the most common type of liposarcoma in children and teens.
• A rare type is termed pleomorphic (meaning the cancer cells look different in size and shape) liposarcoma and makes up only about 5%-10% of liposarcomas. This type can be very aggressive.
• The last type is termed combined, mixed-type, or dedifferentiated liposarcoma, which is a high-grade sarcoma with an increased risk of metastasis.

Once the tumor has been typed, it is usually staged to determine the extent of spread of the tumor at the time of diagnosis. The stages range from I to IV, with IV representing the most extensive cancer with metastatic spread.

The treatment of liposarcoma is mainly surgical, with the goal to remove the tumor entirely and prevent its recurrence (achieving a cure) by removing all of the tumor cells. In the past, amputation was the surgical option for these tumors in the limbs. Currently, tumors that occur in limbs only require about 5% of patients to undergo amputation. Tumor removal by surgery in other areas of the body is the treatment of choice for liposarcomas. However, many patients are treated by a combination of surgery and radiation therapy. In fact, some patients are given radiation therapy before surgery to shrink the tumor.

Chemotherapy in the treatment of liposarcoma is controversial, and experts in the field consider the question of chemotherapy for liposarcoma to be best addressed on a case-by-case basis. Some investigators consider chemotherapy of liposarcomas to be experimental. Because liposarcomas are relatively rare, your doctor should be a specialist with experience treating sarcomas.

Chemotherapy has been done (for example, using anthracycline drugs) without great success. For unresectable (cannot be treated by surgery) or metastatic liposarcomas, trabectedin and eribulin mesylate have been approved by the U.S. Food and Drug Administration (FDA) to treat the disease in patients who had received a prior anthracycline-based chemotherapy regimen, as both these drugs showed an improvement in progression-free survival as compared to other drugs.

The prognosis of liposarcomas varies with the type and location of the tumors. Extremity tumors that are appropriately treated have a good prognosis as do the well-differentiated types and myxoid type tumors. However, round-cell and poorly differentiated cell types have a poor prognosis with a survival rate of about 50% over five years.

As stated previously, if any mass or lump is noticed near or at a site of trauma, or if you develop any of the late symptoms of a liposarcoma described above, you should contact your doctor immediately. Many conditions other than malignant tumors can cause a mass or lump, and it is important to find out the cause so that appropriate treatment can be given.

Most liposarcomas develop in people with no known risk factors. Consequently, there is no way to prevent liposarcomas other than to avoid exposure to their risk factors listed above.