Liposarcoma vs. lipoma
What is the difference between a liposarcoma and a lipoma?
Answer Section
By Mayo Clinic Staff
A liposarcoma is a cancerous fatty tumor. A lipoma is a noncancerous fatty tumor, which means it is benign. They may look similar on imaging. For example, a well-differentiated liposarcoma can look much like a lipoma. Depending on its location in the body, this type of liposarcoma is also known as an atypical lipomatous tumor. Liposarcomas are treated with surgery if possible. By comparison, lipomas do not need treatment unless they are bothersome.
Liposarcomas look and feel like lipomas but tend to be larger. They may press on nearby parts of the body.
A typical lipoma is a soft, movable lump under the skin. It usually doesn't cause symptoms. Most lipomas under the skin are smaller than 4 inches (10 centimeters).
Some features of the tumors can offer clues, but they cannot always reliably tell the two conditions apart. Both lipomas and liposarcomas in the arms, legs or trunk can be slow growing, painless and well-defined. Both may feel doughy. Appearance and touch alone may not provide a definite diagnosis.
Can a lipoma turn into a liposarcoma?
An ordinary lipoma and a liposarcoma are different kinds of tumors, rather than stages of the same condition. A lipoma rarely changes into a well-differentiated liposarcoma.
Can a liposarcoma be mistaken for a lipoma?
Liposarcoma can closely resemble a lipoma during a physical exam and on imaging. Even advanced imaging does not always clearly separate a benign fatty tumor from liposarcoma.
Healthcare professionals look at several features, including the size and depth of the mass and what it looks like on imaging. Imaging findings that raise concern for liposarcoma include:
- A mass beneath the tissue covering the muscles.
- Thick internal bands called septa that are between tissues.
- Areas that show up when contrast is used.
- A larger tumor.
Depending on the findings, doing a biopsy to look at the tissue sample may be needed to make the diagnosis.
Can ultrasound, CT or MRI tell the difference between a liposarcoma and a lipoma?
Ultrasound can show things such as a mass's size, depth, borders and internal appearance. It may not always tell a lipoma from a liposarcoma because their ultrasound features can overlap. For a superficial soft tissue mass, ultrasound is one of the tests used first.
A CT scan also can show details of a mass. A lipoma has a more uniform density than a liposarcoma.
MRI provides more detail about fatty tumors. Lipomas often have a uniform fat appearance and thin internal septa. Liposarcomas are more likely to have thick or nodular septa. Larger size and deeper location in the body also can point to liposarcoma.
If imaging tests cannot tell whether the tumor is a lipoma or liposarcoma, tissue testing using a biopsy might be needed for diagnosis.
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