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 centimeter 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 yet to be convincingly documented.
The most common type is the "superficial subcutaneous lipoma", i.e. just below the surface of the skin. Most occur on the trunk, thighs and the forearms, although they may be found anywhere in the body where fat is located.
Lipoma of the corpus callosum is a rare congenital condition which may or may not present with symptoms. Lipomas are usually relatively small with diameters of about 1 - 3 centimeters, but in rare cases they can grow over several years into "giant lipomas" that are 10-20 cm across and weigh up to 4-5 kilograms.
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.
Lipomas are normally removed by simple excision. This cures the majority of cases, with about 1-2% of lipomas recurring after excision. 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.
Adiposis dolorosa (Dercum disease), is a rare condition involving multiple painful lipomas, swelling, and fatigue. It is generally seen in obese, postmenopausal women.
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.