lipomes

Lipomas are benign tumors composed of mature adipose tissue. They are usually soft, mobile, painless, and grow slowly. Most lipomas occur in the subcutaneous tissues of the neck, shoulders, back, arms, or trunk, but they can arise in deeper locations such as within muscle (intramuscular lipoma) or internal organs. Variants include angiolipomas, which contain numerous blood vessels and can be painful; spindle cell/pleomorphic lipomas; and myxoid lipomas. Rare forms include hibernoma, a tumor of brown fat.

The exact cause of lipomas is not fully understood. Genetic factors can predispose some individuals, and familial multiple lipomatosis is a recognized hereditary condition. Local trauma has been suggested as a trigger in some cases, but evidence is inconsistent.

Diagnosis is usually clinical. Imaging is reserved for deep or atypical lesions. Ultrasound typically shows a well-defined, hyperechoic or homogeneous lesion consistent with fat. Magnetic resonance imaging is the most informative modality to characterize fat content and to distinguish lipomas from more concerning masses; liposarcomas may show thick septa, nodular non-fatty components, and greater enhancement after contrast. In uncertain cases, a biopsy or excision may be performed to exclude malignancy.

Management is often conservative if the lipoma is asymptomatic. Symptomatic or cosmetically bothersome lipomas are commonly removed by surgical excision; liposuction can be an option for some superficial lesions. Recurrence after complete removal is uncommon, though deep or infiltrative lipomas may recur. The prognosis after removal is excellent, and malignant transformation of lipomas is exceedingly rare.