lipóma

Lipóma, commonly written lipoma, is a benign tumor composed of mature adipose tissue. It is one of the most frequent soft-tissue tumors in adults, typically presenting as a soft, slow-growing, painless lump beneath the skin.

Most lipomas are subcutaneous, mobile, and well circumscribed, usually measuring 1 to 5 centimeters. Variants include angiolipoma (has a vascular component and can be painful), spindle cell lipoma, fibrolipoma, and myolipoma, among others. Deep lipomas can arise in muscle or retroperitoneal spaces and may be harder to detect clinically.

The exact cause of lipomas is unknown. Genetic factors can play a role, especially in familial lipomatosis where multiple lipomas occur. Obesity itself is not considered a direct cause. Rare associations with trauma have been reported, but evidence is inconclusive.

Diagnosis is typically clinical, based on the characteristic features. Imaging, such as ultrasound or magnetic resonance imaging, may be used to assess depth and relation to surrounding structures, particularly for deep or enlarging lesions. A biopsy or surgical excision provides definitive diagnosis, showing mature adipocytes with a fibrous capsule and no signs of malignancy.

Treatment is usually not required for asymptomatic lipomas. Symptomatic, enlarging, or cosmetically undesirable lipomas are commonly removed by simple surgical excision; recurrence after complete removal is uncommon. Infiltrating lipomas, which invade surrounding tissues, may require wider excision due to higher recurrence risk. Malignant transformation to liposarcoma is rare.

Related conditions include lipomatosis (multiple lipomas) and various lipoma subtypes and liposarcoma.