We report two cases of clinically rare angiomyolipomas of the liver and their ultrasonographic appearance. Case 1 was that of a 68-year-old woman with cancer of the transverse colon who had a preoperative ultrasonographic examination that disclosed a hyperechoic knobby tumor in the liver. The tumor had a well-defined, slightly irregular contour measuring 3.5 cm in diameter at the surface of segment 8. It was brighter than the usual hemangioma and had a slight acoustic shadow. A postcontrast CT scan revealed a low-density mass with a clear margin, suggesting a fat component. The density of the marginal part was high. Abdominal digital subtraction angiography showed a markedly hypervascular tumor in the arterial phase and heterogeneous tumor staining in the capillary phase. The transverse colon and part of segment 8 of the liver were resected. Histological diagnosis showed the lesion to be a hepatic angiomyolipoma consisting of mature fat cells, vessels, and smooth-muscle tissues. In case 2, routine physical examination disclosed a hepatic hemangioma in a 40-year-old man. He was admitted to this institution because of epigastralgia. Ultrasonography disclosed a hyperechoic knobby tumor with a well-defined, slightly irregular contour measuring 3.5 cm in diameter at the surface of segment 8 of the liver. This, too, was brighter than usual hemangioma with a clear acoustic shadow, and abdominal CT scan and digital subtraction angiography showed findings similar to those reported in case 1. Both T1- and T2-weighted images showed high intensity on abdominal MRI study. Part of liver segment 8 was resected; the histological diagnosis was hepatic angiomyolipoma. In this
case, there were hepatocytes and foamy macrophages among the fat cells. Ultrasonographic findings of a hepatic angiomyolipoma have been reported to be a hyperechoic knobby tumor with a well-defined and slightly irregular contour. The echogenecity of the tumor is brighter than that of the usual hemangioma, and the tumor sometimes has an acoustic shadow. An acoustic shadow behind a bright hepatic tumor like those described here may provide a clue for diagnosing angiomyolipomas.