A lipoma is a benign tumor composed of fatty tissue.They are the most common form of soft tissuetumor. Lipomas are soft to the touch, usually movable, and are generallypainless. Many Lipomas are small (under one centimeter diameter) but canenlarge to sizes greater than six centimeters. Lipomas are commonly found inadults from 40 to 60 years of age, but can also be found in children. Somesources claim that malignant transformation can occur, while others say thatthis has yet to be convincingly documented.
There are several subtypes of lipoma:
- Angiolipoleiomyoma is an acquired, solitary, asymptomatic acral nodule, characterized histologically by well-circumscribed subcutaneous tumors composed of smooth muscle cells, blood vessels, connective tissue, and fat.
- Angiolipoma is a painful subcutaneous nodule, having all other features of a typical lipoma.
- Chondroid lipomas are deep-seated, firm, yellow tumors that characteristically occur on the legs of women.
- Corpus callosum lipoma is a rare congenital condition which may or may not present with symptoms. Lipomas are usually relatively small with diameters of about 1–3 cm, 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 kg.
- Intradermal spindle cell lipoma is distinct in that it most commonly affects women, and has a wide distribution, occurring with relatively equal frequency on the head and neck, trunk, and upper and lower extremities.
- Neural fibrolipoma is an overgrowth of fibro-fatty tissue along a nerve trunk that often leads to nerve compression.
- Pleomorphic lipomas, like spindle-cell lipomas, occur for the most part on the backs and necks of elderly men, and are characterized by floret giant cells with overlapping nuclei.
- Spindle-cell lipoma is an asymptomatic, slow-growing subcutaneous tumor that has a predilection for the posterior back, neck, and shoulders of older men.
- Superficial subcutaneous lipoma, the most common type of lipoma, lies 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.