Lipomas are benign fatty tumors usually located in subcutaneous tissues, though they may also occur in other locations, such as the internal organs and the internal auditory canal. The masses are comprised primarily of mature adipocytes, which are generally surrounded by a fibrous capsule that makes them easily distinguishable from surrounding tissues. In such cases, the tumors have a doughy feel and can easily be moved around under the surface of the skin.

Occasionally the fat cells of a lipoma will extend out into surrounding tissues, making the tumor significantly less movable. When this extension of adipocytes involves muscle, the tumor is considered a lipoma variant known as an intramuscular lipoma or infiltrating lipoma. Other notable variants include angiolipoma, which is a painful form of the tumor with its own vasculature, adenolipoma, which is distinguished by eccrine sweat glands among the adipocytes, and pleomorphic lipoma, a tumor characterized by giant multinucleated cells intermixed with the normal fat cells.

If a lipoma is unusually large or is found in a place where it can limit movement, treatment may be recommended. Some individuals may elect to have their lipomas treated for cosmetic reasons as well, though the possibility of scarring or other complications should first be considered. Surgical excision is the most typical form of lipoma treatment, but other forms of therapy, including steroid injections and liposuction, are becoming increasingly common. Nevertheless, surgery is still considered the best way to completely cure a lipoma, less than 5 percent of those undergoing the excision procedure experiencing a recurrence of the tumor.

Lipomas can occur in people of any age, but are most common in individuals between 40 and 60 years old. Gender differences in lipoma occurrence have also been noted. Men are more likely than females to experience multiple fatty tumors and women have a higher rate of incidence of solitary lipomas. The cause of lipoma development is not known for certain, but some experts suggest that the tumors may sometimes stem from minor physical injury. Certain diseases and genetic abnormalities, including Gardner’s syndrome, hereditary multiple lipomatosis, and Madelung’s disease, have also been associated with lipomas.

Lipoma at 20x Magnification - Lipomas are typically slow-growing and painless and have virtually no risk of malignant transformation. The tumors are, therefore, often left alone even after diagnosis, which can usually be correctly made simply based upon clinical appearance.