Lipoma

Lipomas are benign fat tissue tumours that typically develop subcutaneously. While they can grow anywhere on the body, lipomas tend to be found around the limbs, back, neck, shoulders, trunk, and forehead.

In very rare cases, lipomas may develop on the muscles, internal organs or brain.

Epidemiology

Lipomas are one of the most common neoplasms; approximately 1 in 1000 people will develop a lipoma during their lifetime.

They can occur in any gender and at any age, but they are most prevalent in 40–60 year olds.

Etiology

The exact etiology of lipoma development is unknown.

However, two-thirds of lipomas show genetic abnormalities, demonstrating a genetic proponent in development.

Certain chromosomal structural rearrangements are associated with lipomas:

12q13-15 region
13q portion loss
6p21-23 region

Types of Lipomas

There are many subtypes of lipomas, including:

Adenolipomas

Occurs in the skin or thyroid and involves eccrine sweat glands.

Conventional

The most common lipoma: superficial, subcutaneous, and made of white adipocytes.

Myelolipomas

Mature adipocyte lipoma involving bone marrow.

Angiolipomas

Often multiple, painful, and made of mature adipocytes and small blood vessels.

Fibrolipomas

Lipoma with focal areas of fibrous tissue that may involve nerves.

Pleomorphic

Mostly seen in elderly men. Adipocytes of various size and shape are present.

Chondroid

Mostly appear on women's legs. Mix of adipocytes, lipoblasts, and immature cartilage.

Hibernomas

Involving brown adipocytes.

Spindle-Cell

Lipomas characterized by elongated adipocytes.

Signs & Symptoms

Lipomas often don't present symptoms and may go unnoticed.

However, sometimes they can become painful if they compress a nerve or grow by a joint.

Lipomas are usually:

Encapsulated (don't spread)
Round or oval in shape (symmetrical)
Moveable when touched
Typically smaller than 2 inches
- Occasionally 6 inches or wider

Treatment

The majority of lipomas do not require any treatment unless they are bothering the patient or need to be removed for a differential diagnosis.

Some lipomas can become painful, restrict movement, or present a cosmetic issue if they grow very large. In these cases, lipomas are typically surgically removed. Alternatively, liposuction may be performed to remove the lipoma when there is connective tissue involvement and the lipoma is soft.

Prognosis

Conventional lipomas are a benign condition that many people have and may not notice. There are rare occasions where lipomas may be a more serious condition:

Growth in internal organs

Despite being benign, lipomas in internal organs may cause painful obstructions and bleeding.

Malignant transformation

Very rare cases of transformation of lipomas into liposarcomas have been reported.