Lipoma on Ultrasound: What Does the Report Mean?

A lipoma on ultrasound means the scan shows a lump whose appearance fits a benign (non-cancerous) collection of fat cells. Lipomas are common, usually soft and slow-growing, and most need no treatment. The report describes what the lump looks like; your clinician combines it with an examination and the lump's history before deciding whether anything more is needed.

This guide is for adults who have had a scan of a lump under the skin and have a report mentioning a lipoma or a 'fatty lesion'. It explains common wording and the questions worth asking. It cannot interpret your own scan or rule out other conditions.

The NHS, Healthdirect and Cleveland Clinic advise getting a lump checked, or rechecked if it was already thought to be a lipoma, if any of the following apply. These signs do not mean cancer, but they are the features clinicians want to know about.

If a lump becomes suddenly very painful, hot and red with fever, or you feel unwell, seek prompt medical care rather than waiting for a routine review.

• The lump is getting bigger, especially if it grows quickly over weeks.
• It feels hard, or it is fixed and does not move under the skin.
• It becomes painful, or pain is new or worsening.
• The skin over it turns red or hot.
• It seems to sit deep, below the skin and fat, rather than just under the surface.

The NHS describes a lipoma as a soft, fatty lump that may move slightly when pressed, is usually painless and grows slowly. Healthdirect calls lipomas soft and 'doughy'. They often appear on the shoulders, back, chest, arms, neck or thighs, and are most common between the ages of 40 and 60.

Healthdirect says a typical lipoma is about 1 cm across but can reach 5 to 10 cm. Cleveland Clinic notes that most are smaller than 2 inches (about 5 cm) in diameter. Most people have only one or two. Having many lipomas can occasionally be linked to a rare inherited condition, so mention it if you have several.

Cleveland Clinic explains that imaging such as ultrasound can help tell a lipoma apart from a cyst and show how deep the lump is, whether it contains blood vessels and whether it presses on nerves or other tissue. A report may describe the lump's size in three directions, its depth, its edges and whether it sits in the fat under the skin or within muscle.

Words such as 'well defined', 'no internal vascularity' or 'in keeping with a lipoma' generally mean the appearance fits a simple lipoma. Wording such as 'indeterminate', 'deep to the fascia', 'heterogeneous' or 'MRI recommended' means the radiologist could not be confident from ultrasound alone. Ask the clinician to explain any phrase you do not understand rather than guessing.

Lipomas themselves are benign. The concern is a different, rare tumour that can look similar. Healthdirect notes that some lumps that look like lipomas can be cancerous, such as liposarcomas, and Cleveland Clinic says liposarcoma needs to be ruled out because its signs can resemble those of a lipoma.

The NHS describes a soft tissue sarcoma lump as usually solid, painless and hard to move under the skin, often deep, and continuing to grow. Lumps are common and most are not sarcoma. Still, these features are why a deep, firm or enlarging lump is usually examined more closely rather than labelled a lipoma on appearance alone.

Many small, soft lumps just under the skin are diagnosed by examination, sometimes with ultrasound. Healthdirect and Cleveland Clinic both list MRI, CT and biopsy as possible next tests when the diagnosis is not clear. Healthdirect notes that pain, rapid growth or a lump fixed under the skin can prompt referral to a specialist.

MRI gives detailed pictures of fat and the surrounding tissue, which helps when a lump is large, deep, within muscle or not typical on ultrasound. Cleveland Clinic notes that for deep intramuscular lipomas, imaging is the main tool and a needle biopsy may confirm that the lump is not a soft tissue cancer. The National Cancer Institute describes core needle biopsy guided by ultrasound, CT or MRI as a common way to sample a suspicious lump. Guidance does not set one size limit that applies to everyone, so ask what made your clinician choose, or not choose, further tests.

Most lipomas do not need treatment. Healthdirect and the NHS say removal is usually considered if a lump is growing, causing pain or symptoms because of its position, needed for diagnosis, or bothersome in appearance. Removal is usually surgical, and a removed lump may be sent to a laboratory to confirm what it is. Availability of removal for cosmetic reasons differs between health systems.

Bring the written scan report and note when you first noticed the lump and whether it has changed. These questions can help.

• Does the scan clearly show a simple lipoma, or was any part uncertain?
• How deep is the lump, and is it in the fat under the skin or within muscle?
• Would MRI or a biopsy add anything in my case, and why or why not?
• Should the lump be measured again, and if so, when and by whom?
• What changes in size, feel or pain should make me come back sooner?
• Is removal an option, and what would the benefits and risks be?

On SameCase, patients and verified doctors share de-identified cases. Seeing how other people's lipoma reports were worded, and which ones led to MRI, a biopsy or simple reassurance, can help you think of questions about your own lump. Doctors' comments on similar cases may point to details worth raising, such as depth or growth.

Other people's cases cannot tell you what your lump is. Use them to prepare, then discuss your own scan and examination with your clinician.