Lipoma
Key points
- Lipoma: the commonest soft tissue tumour, a benign proliferation of mature adipocytes enclosed within a thin fibrous capsule, arising in the subcutaneous tissue.
- Classic examination findings: soft, mobile, non-tender, and often lobulated, with the skin freely mobile over the lump rather than tethered to it - together sufficient for a confident clinical diagnosis in most cases.
- Distribution: most often the trunk, neck, shoulders and proximal limbs, though a lipoma can arise wherever fat is present, including rare deep intramuscular locations.
- Diagnosis: usually clinical; imaging (ultrasound or MRI) is reserved for atypical features, deep or large lesions, or genuine diagnostic uncertainty.
- Variants: angiolipoma (painful, vascular), familial multiple lipomatosis, Dercum disease (multiple painful lipomas) and Madelung disease (symmetric lipomatosis, strongly associated with alcohol excess).
- Management: reassurance and no treatment for the great majority; excision is reserved for symptomatic, cosmetically troubling, rapidly growing, or diagnostically uncertain lesions.
- Key differential: liposarcoma, a rare malignant soft tissue tumour that arises independently rather than from malignant change within an existing lipoma, but which can closely resemble one clinically.
- Red flag: a lump larger than 5cm, deep to the deep fascia, rapidly growing, painful, or fixed to surrounding structures needs urgent imaging and referral under the suspected sarcoma pathway rather than reassurance.
Introduction
A lipoma is a benign tumour of mature adipose tissue and is, by a wide margin, the commonest soft tissue tumour encountered in clinical practice. Most people who have one will have noticed it themselves as a slowly enlarging, painless lump, most often on the trunk, neck or a proximal limb, and the diagnosis is usually straightforward on examination alone.
The clinical importance of lipoma lies less in the lesion itself, which needs no treatment in the great majority of cases, and more in reliably distinguishing it from its rare malignant counterpart, liposarcoma, and from the handful of other lumps that can present in a similar way. Getting the examination findings right, and knowing which features do not fit a straightforward lipoma, is the practical skill this topic tests.
Aetiology and pathophysiology
A lipoma consists of mature, normal-appearing adipocytes, arranged in lobules and surrounded by a thin fibrous capsule that separates it from the surrounding subcutaneous fat - the capsule is what gives a lipoma its characteristic mobility and well-defined edge on palpation.
Most lipomas are sporadic, but a genetic contribution is well documented: a significant proportion show rearrangements involving the HMGA2 gene on chromosome 12, a transcription factor involved in cell growth regulation, providing a specific molecular explanation for the abnormal, localised adipocyte proliferation.5
Familial multiple lipomatosis is an autosomal dominant condition in which numerous lipomas develop, typically on the trunk and limbs, from adolescence or early adulthood onwards, and is one of several distinct multiple-lipoma syndromes discussed further below.6
Risk factors
- Middle age - most lipomas present between 40 and 60 years old
- Family history - a first-degree relative with lipomas, particularly relevant in familial multiple lipomatosis
- Obesity - a weak and inconsistent association; lipomas are not simply a consequence of excess adiposity, and lean patients develop them too
- Previous trauma to the site - anecdotally reported (sometimes called a 'post-traumatic lipoma') but the causal relationship is not well established
- Certain genetic syndromes - multiple lipomas are a feature of Cowden syndrome, Gardner syndrome, and Madelung disease, discussed below
Clinical features
A typical lipoma is a soft, smooth, mobile, painless subcutaneous swelling, usually 1-5cm across, that has grown slowly over months to years. It is most commonly found on the trunk, neck, shoulders and proximal limbs, though it can occur wherever fat tissue is present.1
| Variant | Features |
|---|---|
| Angiolipoma | A subtype containing a prominent vascular component; unlike ordinary lipomas, these are often tender or painful, and typically occur on the forearms in young adults |
| Familial multiple lipomatosis | Autosomal dominant condition with numerous subcutaneous lipomas, usually on the trunk and limbs, from adolescence or early adulthood |
| Dercum disease (adiposis dolorosa) | Multiple painful lipomas, most often in obese peri- or post-menopausal women, associated with fatigue and joint pain; the pain is often disproportionate to the size or number of lesions7 |
| Madelung disease (multiple symmetric lipomatosis) | Symmetrical, diffuse fatty deposits around the neck and upper trunk, strongly associated with chronic alcohol excess, predominantly affecting middle-aged men from the Mediterranean region8 |
Clinical examination
- Consistency - soft and doughy, sometimes lobulated on careful palpation
- Mobility - freely mobile beneath normal, unattached overlying skin, which itself moves independently over the lump
- Tenderness - typically painless; tenderness suggests an angiolipoma, Dercum disease, or an alternative diagnosis
- Size and growth rate - most are a few centimetres and grow very slowly over years; document size at first assessment to allow objective comparison at review
- Number and distribution - a single lesion versus multiple lipomas, which raises the possibility of a familial or syndromic lipomatosis
- Fixation to deep structures or overlying skin - a lipoma should not be tethered to skin or fixed to underlying muscle or fascia; either finding should prompt reconsideration of the diagnosis
Differential diagnosis
- Epidermoid cyst - more superficial, often with a visible central punctum, and typically firmer and less mobile than a lipoma
- Liposarcoma - can look and feel similar, but is more often larger, deeper (below the deep fascia or intramuscular), faster growing, and occasionally painful; discussed further under Red flags
- Abscess - warm, tender, fluctuant, with signs of surrounding inflammation, unlike the painless, non-inflamed lipoma
- Ganglion cyst - firmer and typically near a joint or tendon sheath, most often the wrist
- Neurofibroma - can be soft and mobile but often shows a 'buttonhole' sign (invaginating on pressure) and may be associated with café-au-lait patches if neurofibromatosis type 1 is present
- Sebaceous (pilar) cyst on the scalp - firmer, without the same lobulated feel
Investigations
A lipoma with classic examination findings needs no investigation. Imaging is reserved for lesions with atypical features or genuine diagnostic uncertainty.2
- Ultrasound - a reasonable first-line investigation for a lump that is larger, deeper, or otherwise atypical, and can help distinguish a simple lipoma from a more complex or vascular lesion
- MRI - the investigation of choice for a lump with any red flag feature (below), since it best characterises depth, size and any invasion of surrounding structures, and is the standard pre-referral investigation in suspected soft tissue sarcoma pathways3
- Core needle or excision biopsy - performed if imaging is inconclusive or shows features atypical for a simple lipoma, ideally arranged through a specialist sarcoma service rather than as an unplanned excision in primary care
Management
- Reassurance and no treatment - appropriate for the great majority of lipomas with classic, reassuring examination findings
- Simple excision - for lesions that are symptomatic (catching on clothing, causing discomfort), cosmetically bothersome, or where histological confirmation is wanted
- Liposuction - an option for larger or multiple lesions, particularly in familial multiple lipomatosis, though it does not remove the fibrous capsule and can therefore carry a higher recurrence rate than formal excision
- Specialist referral rather than primary care excision for any lesion with red flag features, so that imaging and, if needed, biopsy can be arranged before any surgical intervention risks contaminating tissue planes in an undiagnosed sarcoma
Complications
- Local recurrence after excision - uncommon if the capsule is fully removed, more likely after incomplete excision or liposuction
- Cosmetic concern, particularly for facial, visible, or rapidly enlarging lesions
- Mechanical symptoms - discomfort from a lipoma catching on clothing, or rarely, nerve or vascular compression from a deep or intramuscular lipoma
- Diagnostic delay if red flag features are dismissed - the principal serious complication in this topic is not the lipoma itself but a missed liposarcoma
Red flags
Prognosis
Lipomas are entirely benign and, once correctly identified, carry an excellent prognosis with no risk to life or long-term health. They very rarely cause any complication beyond local cosmetic or mechanical nuisance, and malignant transformation of an existing lipoma into liposarcoma does not occur - the two are separate entities from the outset, not points on the same disease spectrum.
Following excision, recurrence at the same site is uncommon provided the capsule is completely removed, and most patients need no further follow-up. The main determinant of a good long-term outcome across this topic is not treatment of the lipoma itself, but making sure that any lump with an atypical feature is correctly identified and referred rather than reassured, so that a small number of significant sarcomas are not missed among the very large number of harmless lipomas seen in practice.
References
- DermNet NZ. Lipoma. Available here
- Salam GA. Lipoma excision. American Family Physician. 2002. Available here
- NICE NG12. Suspected cancer: recognition and referral. 2015, updated 2023. Available here
- Gerrand C, Athanasou N, Brennan B et al. UK guidelines for the management of soft tissue sarcomas. Clinical Sarcoma Research. 2016. Available here
- Ashar HR, Fejzo MS, Tkachenko A et al. Disruption of the architectural factor HMGI-C: DNA-binding AT hook motifs fused in lipomas to distinct transcriptional regulatory domains. Cell. 1995. Available here
- Charifa A, Azmat CE, Badri T. Lipoma. StatPearls. 2023. Available here
- Hansson E, Svensson H, Brorson H. Review of Dercum's disease and proposal of diagnostic criteria, diagnostic delay, disease staging and classification of pain. Orphanet Journal of Rare Diseases. 2012. Available here
- Enzi G, Busetto L, Ceschin E et al. Multiple symmetric lipomatosis: clinical aspects and outcome in a long-term longitudinal study. International Journal of Obesity. 2002. Available here
This article is written for revision and education. It is not clinical guidance and must not be used to make decisions about the care of a patient. Always check current NICE guidance and local protocols.