A 74-year-old woman presented to a Level-1 trauma center following a motor vehicle accident. A computed tomography (CT) of the abdomen was performed (figure 1).
Prepared by Aspan S. Ohson, MD and Stuart E. Mirvis, MD,
FACR, from the Department of Radiology, University of Maryland
School of Medicine, Baltimore, MD.
A 74-year-old woman presented to a Level-1 trauma center
following a motor vehicle accident. A computed tomography (CT) of
the abdomen was performed (figure 1).
A contrast-enhanced CT of the abdomen reveals a 5-cm mass in the
posterior segment of the right hepatic lobe composed mostly of
fatty tissue with some internal soft tissue stranding the hepatic
lobe (figure 1).
Hepatic angiomyolipoma is a rare entity with only 70 cases
reported in U.S./Japanese literature during the past 25 years.
It is considered a benign mesenchymal tumor, often with a
distinguishing fatty component.
Unlike the more common renal angiomyolipoma, which is associated
with tuberous sclerosis in 40% to 50% of cases, hepatic
angiomyolipoma is usually solitary. In addition, intratumoral
hemorrhage, a common complication in renal angiomyolipoma, has not
been reported in its hepatic counterpart.
Angiomyolipoma, as its name implies, is composed of varying
proportions of fat, blood vessel, and muscle, though the proportion
of fat can be smaller in the hepatic form than in its renal
analogue. In a study by Goodman and Ishak,
fat occupied ¾ 10% of cut sections in 42% of hepatic
Differential considerations include lipoma, adenoma, focal fatty
infiltration, pseudolipoma, and metastatic neoplasms, such as
malignant teretoma and liposarcoma. Among fat-containing hepatic
lesions, however, the most important and common malignant diagnosis
that must be distinguished from angiomyo-lipoma is hepatocellular
carcinoma with fatty metamorphosis. Usually, hepatocellular
carcinomas are well differentiated and therefore hypovascular; in
contrast, an angiomyolipoma is hypervascular.
Ahmadi et al
attempted to differentiate angiomyolipoma from hepatocellular
carcinoma based on dynamic contrast CT where angio-myolipoma showed
early and prolonged enhancement (>4 min) with delayed peak
enhancement at 40 to 80 seconds; as opposed to hepatocellular
carcinoma that has peak enhancement at 10 seconds and absent or
minimal delayed enhancement. Differentiation of angiomyolipoma from
cavernous hemangioma can also be made based on the former's earlier
Similiarly, Sakamoto et al
described MRI studies showing extensive enhancement on
gadolinium-enhanced images. In addition, fat could be seen with
great sensitivity on T1-weighted images as high-signal intensity.
Differentiation from hepatocellular carcinoma with fatty
metamorphosis can also be made based on the angiomyolipomas
prolonged tumor enhancement (>6 min) relative to hepatocellular
Angiomyolipomas have a benign course, making preoperative
diagnosis important prior to performing a major surgery, such as a
hepatic wedge resection. In the recent past, differentiation of
angiomyolipoma from hepato-cellular carcinoma with fatty
metamorphosis was problematic, requiring biopsy or surgical
resection. However, the introduction of improved diagnostic
protocols with CT and MRI should permit accurate imaging diagnosis
without the need for tissue sampling.