What Is a Lipoma?

A lipoma is a benign tumor (non-cancerous growth) that occurs on or under the skin. It is made of fat cells (adipocytes) and feels soft and rubbery. Lipomas may appear anywhere on your body. They're usually not painful.

Lipomas are the most common abnormal growth seen by healthcare providers. About 1% of people will develop a lipoma at some point in their lives. However, lipomas may be more common than the recorded data because they are often small and not bothersome.

Lipomas generally do not require treatment, but they can be surgically removed if desired. Steroid injections and liposuction are other treatment options.

Types

Healthcare providers classify lipomas based on where they occur in the body or by how the tumor cells look under a microscope.

Lipoma types include:

• Conventional lipoma: The most common type of lipoma, composed of mature white fat cells (fat cells that store energy in large droplets)
• Hibernoma: Composed of brown fat cells (fat cells that store less energy and burn more calories than white fat cells)
• Fibrolipoma: Fat cells and stringy, fibrous tissue
• Angiolipoma: Mature fat cells combined with many small blood vessels
• Myelolipoma: Fat cells and blood cell-producing material similar to bone marrow (the spongy center of bones)
• Myolipoma: Mature fat and smooth muscle
• Spindle cell lipoma: Fat and rod-shaped cells called spindle cells
• Pleomorphic lipoma: Fat cells of many different shapes and sizes, including giant-sized fat cells
  
• Adenolipoma: Fat cells and sweat glands
• Giant lipoma: Weighs over one kilogram (kg) or is more than 10 centimeters (cm) wide

Most lipomas are superficial, meaning they grow on the surface of the skin or in subcutaneous tissue just beneath the skin. Lipomas can also develop in soft tissue deeper under the skin, including muscle tissue. Deeper lipomas can grow quite large before they're noticed.

Researchers continue to develop tests that help differentiate different kinds of lipomas from one another and from some types of cancer.

Lipoma Symptoms

Lipomas are usually round or oval-shaped. Fat cells in lipomas are often clumped together in bigger balls called lobes, and the entire fatty growth is contained by a fibrous sack called a capsule.

Most lipomas exist without any symptoms. A soft, lumpy area, typically less than two inches wide, may be felt or seen on the surface of or underneath the skin. It's often slow to grow and can be moved slightly underneath the skin.

A lipoma can occur anywhere on your skin and in most organs. About 5% of people with lipomas have multiple lipomas.

Most lipomas appear in the following areas:

• Legs (especially the thighs)
• Buttocks
• Arms
• Shoulders
• Upper Back
  
• Head and neck
  

Lipomas tend to stay the same size, and they are not generally painful. However, they can press on a nearby structure like a nerve or blood vessel which can cause pain in the area.

This photo contains medical imagery.

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Lipoma Causes

The exact cause of lipomas is not known or understood. There's no definitive proof that chemicals or radiation exposure can cause them. Some types might be genetic, but gender and ethnic background do not seem to be factors. Researchers continue to study general risk factors to better understand who might develop lipomas.

Risk Factors

Anyone can develop a lipoma. They typically appear once people have reached adulthood, particularly between the ages of 40-60.

A lipoma may develop after an injury or physical trauma to an area. Other possible risk factors include:

• Alcohol use disorder (AUD)
  
• Liver disease
• Glucose (sugar) intolerance (GI), a condition caused by hyperglycemia (high blood sugar)
• Having obesity

Diagnosis

Lipomas are commonly identified by a primary care provider or other general healthcare provider. The provider may be able to identify a lipoma during a physical assessment by looking at and feeling your lump. They will check its size, consistency, and mobility (whether or not it moves and how).

A biopsy is required to confirm whether or not a tumor is a lipoma. It can also help determine the type of lipoma. For a biopsy, your healthcare provider will take a small tissue sample and examine it under a microscope.

Additional lab testing may be needed, especially if there are concerns about the initial biopsy results. Testing might include imaging tests like:

• Ultrasound: A technology that uses sound waves to generate images (sonograms)
• X-ray: A medical imaging procedure that uses radiation to generate two-dimensional images
• Computed tomography (CT) scan: A medical imaging procedure that uses radiation to generate three-dimensional images
• Magnetic resonance imaging (MRI): A medical imaging procedure that uses a strong magnetic field and radio waves to generate images (usually two-dimensional)

The imaging test ordered may depend on the size, shape, and location of the mass. Each test creates a different type of visual image of the lump and helps the provider make a diagnosis. Imaging studies can also be helpful in understanding which structures are near the lipoma and how much blood flow the area receives.

Imaging tests probably won't be necessary if the lipoma is superficial (on or near the surface of your skin).

Treatment

Lipomas often don't require treatment. These benign tumors do not spread to other areas of the body or enter nearby tissues.

If you do not pursue treatment, you will want to monitor your tumor for any changes and have your healthcare provider recheck it regularly.

Your provider may suggest treatment if the lipoma grows rapidly or causes pain. You may also choose to treat it for cosmetic reasons. Lipomas are usually treated by a dermatologist, general surgeon, or plastic surgeon.

The most common treatment options for lipomas include:

• Excision: Surgical removal of the entire tumor and the surrounding sack or capsule. Excision is the most common treatment and the only way to remove the entire lipoma.
• Liposuction: Vacuum-like removal of most of the fat cells. Liposuction might be used to remove large lipomas.
• Corticosteroid injection: Inserting a corticosteroid (anti-inflammatory medication) into the mass with a needle. This can help reduce the size of the lipoma, especially if it's smaller than one inch wide. Injections rarely eliminate a lipoma.
  

Removing the entire capsule reduces the likelihood of regrowth. This is easier for subcutaneous lipomas (just under the skin) because they're typically not attached to connective tissue. If you are considering lipoma removal, ask your provider about the risks and benefits of the procedure, the anticipated recovery time, and similar other cases they have performed.

A lipoma is generally considered "cured" once it has been fully removed. It will likely not return.

Prevention

There are no proven ways to prevent a lipoma from occurring or slow its growth. Fortunately, lipomas are usually benign and painless.

Living With Lipomas

Lipomas are generally considered harmless. Most people seek treatment because they don't like the appearance of a lipoma, especially if it's on the face, neck, or other highly visible area. Excision is the most common treatment option, but other options include liposuction and corticosteroid injections to reduce the size of the lipoma.

Researchers continue to explore types of lipomas, their causes, and guidelines for when and how to treat them. 

Reach out to a healthcare provider if you have a large growth or experience discomfort. Lipomas are generally not cancerous, but other tumors may have a similar appearance and may require rapid removal or other treatment.