Usually, treatment of a lipoma is not necessary, unless the tumor becomes painful or restricts movement. They are usually removed for cosmetic reasons, if they grow very large, or for histopathology to check that they are not a more dangerous type of tumor such as a liposarcoma. This last point can be important as the actual identity of a “bump” is not known until after it is removed and professionally examined.
Lipomas are normally removed by simple excision. The removal can often be done under local anaesthetic, and take less than 30 minutes. 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 regrowth.
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.
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 (so-called “malignant by location”, despite being a benign growth histologically). Malignant transformation of lipomas into liposarcomas is very rare and most liposarcomas are not produced from pre-existing benign lesions, although a few cases of malignant transformation have been described for bone and kidney lipomas. It is possible these few reported cases were well-differentiated liposarcomas in which the subtle malignant characteristics were missed when the tumour was first examined. Deep lipomas have a greater tendency to recur than superficial lipomas, because complete surgical removal of deep lipomas is not always possible.
The presence of multiple lipomas is known as lipomatosis and is more commonly encountered in men. Some superficial lipomas can extend into deep fascia and may complicate excision. Liposarcoma is found in 1% of lipomas and are more likely in lesions of the lower extremities, shoulders and retroperitoneal areas. Other risk factors for liposarcoma include large size (>5 cm), associated with calcification, rapid growth and/or invasion into nearby structures or through fascia into muscle tissue.
In veterinary medicine
Lipomas occur in many animals, but are most common in older dogs, particularly older Labrador Retrievers, Doberman Pinschers and Miniature Schnauzers. Overweight female dogs are especially prone to developing these tumors and most older or overweight dogs have at least one lipoma. In dogs, lipomas usually occur in the trunk or upper limbs. Lipomas are also found less commonly in cattle and horses, and rarely in cats and pigs. However, a pedunculated lipoma can cause entrapment and torsion of the intestine in horses, causing necrosis, colic, and possibly death. The intestine becomes wound around the stalk of the lipoma and loses blood supply.