Angiomyolipoma of the liver: a collective review

This review summarizes the clinical and pathological findings of 52 cases of hepatic angiomyolipoma to discern and establish the most pertinent clinical and pathologic characteristics of the tumor. The disease was symptomatic in 60% of the patients. Abdominal pain or distress was the most common symptom, appearing in 37% of the patients, followed by malaise and upper abdominal mass or hepatomegaly. Of the 52 patients, only three (5.8%) showed associated tuberous sclerosis. Antemortem diagnosis of the tumor has been made with increasing frequency with the recent advent of computed tomography (CT) and ultrasound (US). The tumor was usually visualized as a hyperechoic mass by US imaging and as a low density mass less than -20 Housefield units by CT, and was hypervascular on angiography. The tumor was usually yellow to light tan, depending on the amount of fat tissue. Histologically, the tumor was characterized by an admixture of mature fat cells, blood vessels, and smooth muscle cells, with occasional foci of extramedullary hematopoiesis. The amount of smooth muscle component varied and often exhibited hypercellularity, pleomorphism with occasional bizarre giant cells, and moderate motitic activity. These features are considered conducive to an erroneous diagnosis of malignant tumor. However, since no malignant counterpart has been reported, it can easily be accurately differentiated histologically, if one is aware of the entity and can identify the three components of the tumor; blood vessels, smooth muscle cells, and fat. With regard to the histogenesis of angiomyolipoma, primitive mesenchymal cells around blood vessels may be the precursor cells.