Lipoma: is it dangerous, and should it be removed?

What is a fatty lump (lipoma)?

A fatty lump, known medically as a lipoma, is one of the most common benign lumps that occurs in the body's soft tissues. It consists of a collection of mature fat cells, often surrounded by a thin fibrous capsule.

Lipomas typically develop in the subcutaneous tissue and can be found anywhere on the body, but are most frequently seen on the torso (trunk), neck, shoulders, and arms.

Typical Characteristics

Lipomas tend to share a set of features that your doctor will weigh during a clinical examination. None of these signs stands alone, but together they build a clear picture:

• Soft and elastic: The lump often feels soft or rubbery to the touch.
• Freely mobile: You can typically push the lump slightly under the skin. It is usually not attached to the deeper tissue.
• Painless: The lump itself does not usually hurt.
• Slow growth: It typically grows slowly over months or years.

If a lump shows these features, that supports a lipoma. The diagnosis, however, is made by a doctor based on the overall picture, not on a single trait.

Why do lipomas occur?

The reason why some people develop lipomas is not fully understood. It is not accurate to say that lipomas develop because someone is overweight or leads an unhealthy lifestyle. Some case series report that lipomas occur somewhat more often in people who are obese, but this is a statistical association, not proof that diet or lifestyle causes the lumps. A lipoma also does not shrink with weight loss the way ordinary fat tissue can.

In some cases, there may be a hereditary component. A proportion of people who develop a lipoma go on to develop further lumps over time, and there are rare hereditary conditions in which numerous lipomas form.

When should you see a doctor? (Warning signs)

The vast majority of lipomas are harmless and require no action. However, it is important to see a doctor if you find a new lump or if an existing lump changes.

No single finding decides whether a lump needs further investigation. Your doctor will weigh a combination of factors:

• Size: Larger lumps carry more weight in the assessment than small ones.
• Depth: A lump that sits deep under the skin or within muscle deserves more attention than one lying just below the skin.
• Growth: Rapid or newly noticed growth is a warning sign.
• Pain: New pain or tenderness, possibly because the lump is pressing on a nerve.
• Consistency: A firm, fixed or lumpy mass carries more weight than a soft, mobile one.

A size of 5 cm or more, a deep location below the fascia, fixation to the underlying tissue and rapid growth are described as risk features in the international guidelines for soft tissue tumours (ESMO-EURACAN-GENTURIS, 2021) and in a review in American Family Physician (Achar et al., 2022). They are not cancer diagnoses in themselves, but they increase the need for medical assessment, imaging or referral.

Your doctor will perform a clinical examination. Whether an ultrasound scan, an MRI scan or a referral is needed depends on the findings, on how certain the clinical assessment is, and on local practice. There is no single investigation used for every lump.

Treatment and Management

As the large majority of lipomas are benign, observation is a common recommendation, as long as the lump does not cause discomfort and there are no findings that argue against a typical lipoma.

Treatment may be considered if:

1. The lump is painful or interferes with the function of surrounding tissue.
2. The lump poses a cosmetic nuisance for the patient.
3. There is uncertainty about the diagnosis, for example because the lump does not behave like a typical lipoma.

Surgical Removal

Selected superficial lipomas can be removed at the clinic as a minor operation under local anaesthesia after an individual assessment by Kirurgen.dk. How much tissue is removed depends on the location and appearance of the lump. Whether the removed tissue is sent for microscopic examination is decided from the findings, the degree of diagnostic uncertainty and the applicable procedure.

Note regarding cosmetic concerns: Referral practice for surgical removal of small, cosmetically bothersome lipomas without physical symptoms varies between public hospitals, and in many places lumps with symptoms or an uncertain diagnosis are prioritised. The possibility of a public referral depends on a specific medical assessment. Some patients therefore choose to be treated by a surgeon in private practice or a dermatologist.

Sources

Gronchi A, et al. Soft tissue and visceral sarcomas: ESMO-EURACAN-GENTURIS Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2021;32(11):1348-1365. PubMed DOI

Achar S, et al. Soft Tissue Masses: Evaluation and Treatment. Am Fam Physician. 2022;105(6):602-612. PubMed

Supplementary source: Charifa A, Azmat CE, Badri T. Lipoma Pathology. StatPearls, updated 2023. Read the StatPearls chapter on lipoma at NCBI Bookshelf