Lipoma (fatty tumor): what it is and what it looks like

A lipoma is a benign formation of adipose tissue that grows under the skin. In everyday speech it is called a fatty tumor; scientifically it is a lipoma (from Greek λίπος, "fat") or a fatty tumor. Below are the definition, appearance, causes, and examination procedure.

What a lipoma is and why it is called a fatty tumor

A lipoma is a benign connective-tissue tumor that develops in the layer of loose subcutaneous connective tissue and can extend deeper between muscles and vascular bundles all the way to the periosteum. Benign tumors are not cancer: they grow only in one place and do not spread to other parts of the body. The name "fatty tumor" reflects the composition of the nodule — it is built from adipose tissue. Such formations are common.

What a fatty tumor under the skin looks and feels like

A subcutaneous fatty tumor is identified as a soft, doughy nodule. It is described as soft and doughy to the touch, ranges in size from a pea to several centimeters, shifts slightly under the skin when pressed, is usually painless, and grows slowly. The nodule appears anywhere on the body, more often on the shoulders, chest, arms, back, buttocks, and thighs; it is also possible on the forehead. A nodule cannot be assessed from a photograph: formations that look similar externally have different natures. When removed, a lipoma is usually enucleated whole (enucleation).

Why lipomas appear

There is an opinion that the main role is played by metabolic changes caused by a deficiency of regulatory protein enzymes, that is, enzymopathy. The cause of the enzymopathy is linked to duplication of the long arm of chromosome 12 (12q13-15), where the loci of the TAG lipase protein gene are located; the only function of this protein is to break down fats into energy and water. In other words, lipomas grow not because of excessive accumulation of fat in adipocytes, but because the pathways for its breakdown are blocked. Familial lipomatosis is inherited in an autosomal dominant manner and manifests at a young age. This is a description of a hypothesis, not an established mechanism for each individual case.

Diffuse lipoma and other forms

Diffuse lipoma (lipoma diffusum) is an accumulation of grape-like masses of fat without sharp boundaries; it is in most cases associated with so-called giant growth, when one or several limbs reach enormous sizes. In Kazaryan's classification, a distinction is made between perineural lipoma (surrounds nerves, is always painful, and is difficult to remove), intermuscular lipoma (grows through muscles and recurs if incompletely removed), and angiolipoma (more often found in the kidneys; the cutaneous form is a dense, painless subcutaneous nodule on the limbs, as a rule in mature men).

How a doctor distinguishes a lipoma from other formations

Usually a doctor can identify a lipoma on examination. If there are doubts, the patient is referred for scanning. A lipoma can be difficult to distinguish from an atheroma, a hygroma, lymphadenitis, and other benign skin neoplasms. In rare cases, a nodule under the skin turns out to be a sign of a more serious disease. A lipoma usually does not transform into cancer, but lipomas of the subcutaneous fat, although quite rarely, do transform into malignant neoplasms of connective tissue — liposarcomas; in the breast, liposarcoma is an extremely rare phenomenon, but a liposarcoma there can grow rapidly and deform the breast.

When a fatty tumor should be shown to a surgeon

The very fact of a nodule appearing anywhere on the body is a reason for examination. The following situations are singled out separately:

• the nodule is painful, red, or hot to the touch;
• the nodule is hard and does not shift;
• the nodule is increasing in size;
• the formation is bothersome because of its location.

Lipomas are harmless and usually do not require removal. They are removed if the formation is growing or causing symptoms because of its location; the removed nodule may be sent to a laboratory to check that it is a lipoma. A large lipoma is removed also for aesthetic reasons. The surgeon assesses the size, density, and mobility of the nodule and the condition of the skin above it; if in doubt, imaging is ordered.

A lipoma by itself is not a reason to call an ambulance; 103/112 — for a life-threatening condition (according to the general signs of emergency care).

The material is for reference and does not replace a doctor's consultation: the decision on examination and testing is made by the doctor during an appointment.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer