Liposarcoma

Liposarcoma vs lipoma

Lipomas are very common benign fatty lumps. Liposarcomas are rare. Features that suggest a lump needs investigation for sarcoma:

NICE and other guidance recommend urgent imaging for soft tissue lumps that are growing or larger than 5 cm.

Types of liposarcoma

Symptoms

• a painless lump that slowly grows, usually in the thigh or behind the knee. See leg lump or mass
• abdominal swelling, fullness, early satiety or vague pain from a retroperitoneal tumor, which can grow very large before causing symptoms
• leg swelling or numbness if a tumor presses on vessels or nerves
• weight loss or tiredness in advanced disease

Causes and risk factors

The cause is usually unknown. Liposarcomas are not caused by lipomas turning into cancer. Specific gene changes are found in the tumors (for example MDM2 amplification in well-differentiated and dedifferentiated types, and a DDIT3 gene fusion in myxoid liposarcoma), but these are not usually inherited. Previous radiation therapy is a rare risk factor.

Diagnosis

• MRI for limb masses; CT for abdominal masses and to check the chest for spread
• Core needle biopsy, ideally performed at or planned by a sarcoma center, so the biopsy path can be removed with the tumor
• Pathology with tests such as MDM2 FISH to confirm the subtype
• additional imaging of the abdomen or spine for myxoid types, which can spread to unusual sites

Care at a specialist sarcoma center is strongly recommended, as outcomes are better with experienced multidisciplinary teams.

Treatment

• Surgery: the main treatment, removing the tumor with a margin of healthy tissue. Limb-sparing surgery is possible in most cases. Retroperitoneal tumors may require removing nearby organs.
• Radiation therapy: before or after surgery for many limb tumors, especially larger or higher-grade ones. Myxoid liposarcoma is particularly radiation-sensitive.
• Chemotherapy: for high-grade, recurrent or metastatic disease; options include doxorubicin-based regimens, trabectedin and eribulin.
• Clinical trials: testing targeted drugs such as MDM2 and CDK4 inhibitors.

Outlook

Outlook depends on subtype, grade, size, location and whether complete removal is possible. Well-differentiated liposarcoma of the limbs has an excellent outlook, though it can recur locally. Retroperitoneal tumors recur more often because wide margins are hard to achieve. Dedifferentiated and pleomorphic types have a higher risk of spreading. Long-term follow-up with regular imaging is needed, often for 10 years or more.

Frequently asked questions

What is the difference between a lipoma and a liposarcoma?

A lipoma is a common, harmless fatty lump just under the skin, usually small and stable. A liposarcoma is a rare cancer of fat cells that is often deep, larger than 5 cm and growing. Imaging and a biopsy are needed to tell them apart when a lump has worrying features.

Is liposarcoma curable?

Many liposarcomas, particularly well-differentiated tumors in the limbs, are cured with surgery. Higher-grade types and retroperitoneal tumors are harder to treat and more likely to recur, but treatment can still control the disease for long periods.

What is the survival rate for liposarcoma?

Survival varies greatly by subtype. Well-differentiated liposarcoma has a very high 5-year survival, while pleomorphic and dedifferentiated types have lower survival. Your sarcoma team can give the most accurate estimate based on your tumor.

Can a lipoma turn into liposarcoma?

It is thought to be extremely rare or not to happen. A liposarcoma that resembles a lipoma may have been liposarcoma from the start. A "lipoma" that grows, is deep or larger than 5 cm should be imaged.