Posttraumatic lipoma: fact or fiction?

BACKGROUND: Both trauma and lipomas are a common occurrence in surgical practice. Lipomas are usually benign adipose tumors with as-yet unexplained pathogenesis and etiology. A link between soft tissue trauma and the formation of lipomas has been described, with the latter being named posttraumatic lipomas.
METHODS: Twenty-three cases of posttraumatic lipomas in 19 patients treated at our institution between August 2001 and January 2005 were reviewed with regard to medical history, magnetic resonance imaging findings, intraoperative findings, clinical chemistry, and histology.
RESULTS: The mean age of the patients was 50.0 years (+/-15.5). The average time between soft tissue trauma and lipoma formation was 2.6 years (range, 0.5-6.0 years). Sixteen of the 19 patients reported extensive and slowly resolving hematoma formation after the traumatic event. Nine of 23 lipomas were found on the upper extremities, 3 on the lower extremities, 9 on the trunk, and 2 on the face. All tumors were located epifascially. Twenty-two lipomas were removed by simple excision and, in one case, aspiration lipectomy was performed. Pathology demonstrated capsulated and noncapsulated benign adipose tumors in 23 cases. The average body mass index, amounted to 30 kg/m(2) (+/-7.6 kg/m(2)). Seven patients without known bleeding disorders presented with an elevated partial thromboplastin time.
CONCLUSIONS: The pathogenetic link between soft tissue trauma and the formation of posttraumatic lipomas is still controversially discussed. There are 2 potential explanations to correlate soft tissue trauma and adipose tissue tumor growth. The first is the formation of so-called posttraumatic pseudolipomas by prolapsing adipose tissue through fascia resulting from direct impact. A second possibility points toward lipoma formation as a result of preadipocyte differentiation and proliferation mediated by cytokine release following soft tissue trauma and hematoma formation.