A lipoma is a lump under the skin that occurs due to an overgrowth of fat cells. Doctors consider lipomas to be benign tumors, which means that they are non-cancerous growths.
However, people may wish to remove a lipoma that causes pain, complications, or other symptoms. Some people also have concerns about the cosmetic appearance of them.
They can occur anywhere on the body where fat cells are present, but they tend to appear on the shoulders, chest, trunk, neck, thighs, and armpits. In less common cases, they may also form in internal organs, bones, or muscles.
They feel soft and may move slightly under the skin when people press down on them. They usually grow slowly over a period of months or years. Occasionally, people have giant lipomas, which can grow to more than 4 inches.
Doctors do not fully understand the exact cause.
Some people inherit a faulty gene from their parents that can cause them. This is rare and is known as familial multiple lipomatosis.
They can occur more frequently in people with specific medical conditions, such as:
- Gardner’s syndrome
- Cowden syndrome
- Madelung’s disease
- adiposis dolorosa
Researchers have also suggested that some may result from an injury that involves a substantial impact on the area.
A person with a lipoma will typically feel a soft, oval-shaped lump just beneath the skin. They are usually painless unless they affect joints, organs, nerves, or blood vessels. In most cases, they do not cause other symptoms.
A person with a lipoma that occurs deeper under the skin may not be able to see or feel it. However, a deep one may place pressure on internal organs or nerves and cause associated symptoms. For example, a person with one on or near the bowels may experience nausea, vomiting, and constipation.
Lipomas are benign masses of fat cells. However, experts disagree about whether or not they have the potential to become cancerous. A cancerous mass of fat cells is known as a liposarcoma.
Based on research, many experts have concluded that liposarcomas do not develop from lipomas but are, in fact, a different type of tumor. They believe that doctors sometimes mistake liposarcomas for these. Conversely, other experts think that lipomas may contain both cancerous and pre-cancerous cells, but that it is extremely rare for a lipoma to become cancerous.
It is fairly common for a person to develop a lipoma. Experts estimate that around 1 percent of people have one.
People who have a family relative with one or more lipomas have a higher risk of developing this condition. They are also more likely to occur in people aged between 40 and 60 years old.
Other risk factors for developing a lipoma may include:
- high cholesterol
- liver disease
- glucose intolerance
When to see a doctor
People should always tell their doctor if they notice changes in a lipoma or if more lipomas appear. These changes might involve the lipoma:
- increasing in size or suddenly growing very quickly
- being painful
- becoming red or hot
- turning into a hard or immovable lump
- causing visible changes in the overlying skin
They may start by inspecting and feeling the lump. If it is large or painful, the doctor may order tests to check if it is cancerous.
They may use the following tests:
- biopsy, where the doctor will remove a small sample of cells from the lump and examine the tissue under a microscope to look for signs of cancer
- Other scans such as an ultrasound or MRI