lipoma n : a tumor consisting of fatty tissue [syn: adipose tumor] [also: lipomata (pl)]

English

Noun

1. A nonmalignant tumor comprising fat cells.

A lipoma is a benign tumor composed of fatty tissue. These are the most common form of soft tissue tumor. Lipomas are soft to the touch, usually moveable, and are generally painless. Many lipomas are small (under one centimetre diameter) but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults from 40 to 60 years of age, but can also be found in children. Some sources say that malignant transformation can occur, while others claim that this has never been convincingly documented. Lipomas are usually relatively small with diameters of about 1 - 3 centimeters,

Prevalence

Approximately one percent of the general population has a lipoma. These tumors can occur at any age, but are most common in middle age, often appearing in people from 40 to 60 years old. Cutaneous lipomas are rare in children, but these tumors can occur as part of the inherited disease Bannayan-Zonana syndrome.

Causes

The tendency to develop a lipoma is not necessarily hereditary, although it is in a syndrome like familial multiple lipomatosis (where more than one lipoma develops over time.) Hereditary lipomatosis is an autosomal dominant disorder and is a rare condition.

Cases have been reported where minor injuries are alleged to have triggered the growth of a lipoma, called "posttraumatic lipomas". However, the link between trauma and the development of lipomas is controversial. Being overweight does not cause lipomas, however there may be some correlation between being overweight and having lipomas as one genetic study has shown the HMG I-C gene, originally linked to obesity, can also cause lipomas. It was a mice study, but it supports earlier epidemiologic data showing a correlation between defective HMG I-C genes and mesenchymal tumors in humans. Liposuction is another option if the lipoma is soft and has a small connective tissue component. Liposuction typically results in less scarring; however, with large lipomas it may fail to remove the entire tumor, which can lead to re-growth.

There are new methods being developed that are supposed to remove the lipomas without scarring. One of them is removal by the use of injection of compounds that trigger lipolysis, such as steroids or phosphatidylcholine. Another method being developed is the use of ultrasound waves to destroy the lipoma. This can be compared with the removal of kidney stones where ultrasound is used to pulverize the stones.

Prognosis

Lipomas are rarely life-threatening and the common subcutaneous lipomas are not a serious condition. Lipomas growing in internal organs can be more dangerous, for example lipomas in the gastrointestinal tract can cause bleeding, ulceration and painful obstructions. Malignanat transformation of lipomas into liposarcomas is very rare and most liposarcomas are not produced from pre-existing benign lesions,

In other animals

Lipomas occur in many animals, but are most common in older dogs, particularly older Labrador Retrievers, Doberman Pinschers and Miniature Schnauzers. In dogs, lipomas usually occur in the trunk or upper limbs. Lipomas are also found less commonly in cattle and horses, but rarely in cats and pigs.

Benign symmetric lipomatosis (Madelung disease) is another condition involving lipomatosis. It nearly always appears in middle-aged males after many years of alcoholism, although non-alcoholics and females can also be affected.

References

External links

General information

• Patient handout from American Academy of Family Physicians
• Lipoma from New Zealand Dermatological Society

Images

• Illustration from University of Connecticut Health Center
• Esophageal Lipomatosis MedPix Images from Uniformed Services University of the Health Sciences
• Lipoma images from DermAtlas