Lipomas

A lipoma is a benign tumor composed of mature adipose (fat) tissue. It is the most common soft tissue tumor in adults and typically presents as a slow-growing, soft, doughy, and freely movable lump beneath the skin. Lipomas most often occur on the neck, shoulders, back, arms, and trunk, but they can develop almost anywhere. Subcutaneous lipomas are the most common type; less commonly, lipomas can arise within muscle (intramuscular) or beneath fascia (subfascial). Some variants include angiolipomas, which contain more blood vessels, and spindle cell lipomas.

Most lipomas are painless and asymptomatic. They usually do not threaten health, and malignant transformation to liposarcoma is extremely rare. However, a lipoma that grows rapidly, becomes painful, fixed to surrounding tissues, or presents in an atypical location may require further evaluation to exclude liposarcoma. Risk factors include age (commonly in middle age) and a family history of multiple lipomas, as seen in certain hereditary conditions such as familial multiple lipomatosis.

Diagnosis is often clinical. Imaging is not routinely needed but can help when the lesion is deep, large, or its nature is uncertain. Ultrasound typically shows a homogeneous, well-circumscribed lesion with echogenic fat tissue; MRI provides detailed characterization and helps distinguish lipoma from other tumors.

Management ranges from observation to surgical removal. Indications for treatment include symptoms, rapid growth, functional impairment, or cosmetic concerns. Treatment options include complete surgical excision (with capsule) or liposuction for contouring. Recurrence is possible, especially with intramuscular lipomas. Overall prognosis is excellent. See also: liposarcoma.