Angiolipoma is a benign, usually well-circumscribed subcutaneous adipocytic tumor composed of mature adipose tissue admixed with a proliferation of small blood vessels. Clinically, angiolipomas often present as tender or painful subcutaneous nodules, frequently occurring on the forearms, trunk, or upper arms, and may be multiple. Histologically, the lesion resembles a lipoma but contains an increased vascular component, often composed of small capillary-sized vessels. The presence of fibrin thrombi within these vessels is a characteristic diagnostic clue. Cellular or spindle-cell-rich areas may be seen and can raise a differential diagnosis with other vascular or spindle cell lesions, but the combination of mature fat, vascular proliferation, and microvascular fibrin thrombi supports the diagnosis.
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