by Bibianna Purgina, MD FRCPC
December 19, 2025
A lipoma is a benign (non-cancerous) tumour made up of mature fat cells, also called adipocytes. Lipomas are part of a group of tumours known as mesenchymal tumours, which arise from connective tissues such as fat, muscle, or fibrous tissue. Lipoma is the most common type of soft tissue tumour in adults.
Lipomas grow slowly and do not spread to other parts of the body. They are very different from malignant fat tumours, such as liposarcoma.
Where is a lipoma found?
Most lipomas develop just beneath the skin, in a layer called the subcutaneous tissue. Common locations include the neck, upper back, shoulders, upper arms, and upper thighs. Lipomas on the face are uncommon and usually arise deeper, beneath the facial fascia. Lipomas involving the hands, feet, or lower legs are less frequent. Some lipomas develop deeper in soft tissues, but most are superficial and easily felt on physical examination.
What symptoms can a lipoma cause?
Lipomas usually present as a soft, slow-growing, mobile lump under the skin. They are typically painless and may be noticed incidentally or because of cosmetic concerns.
Most lipomas do not cause symptoms. Occasionally, a lipoma may cause discomfort if it presses on a nearby nerve or if it is located in an area exposed to repeated pressure or trauma.
Some people develop multiple lipomas. This may occur sporadically or as part of an inherited condition. In familial multiple lipomatosis, several subcutaneous lipomas develop over time, often beginning in early adulthood. Multiple lipomas can also be seen in rare genetic conditions such as Proteus syndrome and Bannayan–Zonana syndrome.
How common is a lipoma?
Lipoma is the most common mesenchymal tumour in adults. It is most often diagnosed in people in their 40s to 60s and is slightly more common in men. Lipomas are uncommon in children.
What causes a lipoma?
In most cases, the cause of a lipoma is unknown. These tumours are considered idiopathic, meaning they arise without an apparent trigger.
Some people inherit a tendency to develop multiple lipomas. Familial multiple lipomatosis is usually inherited in an autosomal dominant pattern, meaning only one copy of the altered gene is needed—mutations in genes such as PTEN cause other inherited syndromes associated with multiple lipomas.
At the molecular level, many lipomas show changes in a gene called HMGA2, which plays a role in fat cell development. These genetic changes are acquired during life and are not usually inherited.
How is the diagnosis made?
The diagnosis of lipoma is usually made by examining a tissue sample under the microscope. In many cases, the appearance on physical examination and imaging studies is so typical that no biopsy is required unless the lesion has unusual features.
When examined under the microscope, lipomas consist of mature adipocytes that closely resemble normal fat cells. These cells are arranged in lobules and are separated by thin fibrous bands. A thin capsule usually surrounds the tumour.
The fat cells appear uniform, with no abnormal enlargement or darkening of the nuclei. Some lipomas show secondary changes such as fibrosis, small areas of fat breakdown, or myxoid (gel-like) change. Rarely, bone or cartilage may form within the tumour. These variants are called osteolipoma (with bone) and chondrolipoma (with cartilage).
Special stains are usually not required. In some cases, immunohistochemical staining for HMGA2 may help distinguish a lipoma from normal fat, but this is rarely necessary.
What other conditions can look like a lipoma?
The most important tumour to distinguish from a lipoma is an atypical lipomatous tumour, which is a locally aggressive tumour made of fat cells. Unlike lipomas, atypical lipomatous tumours show abnormal features such as enlarged or dark-staining nuclei and atypical stromal cells.
In complex cases, molecular tests looking for MDM2 gene amplification may be performed to exclude an atypical lipomatous tumour.
What is the prognosis for a person with a lipoma?
Lipomas are benign tumours with an excellent prognosis. Complete surgical removal is usually curative. Recurrence is uncommon, occurring in fewer than 5 percent of cases. When recurrence does happen, it is typically slow and non-destructive. Lipomas do not metastasize and do not become cancerous.
Questions to ask your doctor
- Was the lipoma completely removed?
- Is there a chance it could come back?
- Do I need follow-up imaging or exams?
- Could multiple lipomas suggest an inherited condition?
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