Discussion
Hepatic angiomyolipoma
Angiomyolipoma (AML) is a tumor of mesenchymal origin composed of blood vessels, smooth muscle, and adipocytes, as the name suggests. It is most commonly found in the kidneys; hepatic angiomyolipoma (HAML) is rare. While renal AML shows an association with tuberous sclerosis complex in over half of cases, HAML shows such association in only 5% to 15% of cases. HAML occurs predominantly in females and in noncirrhotic patients. While up to 4% of cases show malignant behavior, it is likely an overestimation. Patients are most commonly asymptomatic, as in the presented case. Symptomatic patients usually present with abdominal discomfort.
On CT and MRI, HAML is seen as a well-defined solitary intrahepatic mass with smooth or lobulated margins. The appearance may be variable depending on the composition of vasculature, smooth muscle, and fat; intralesional fat is seen in only 50% to 60% of cases. HAML typically shows heterogeneous arterial hyperenhancement with areas of washout on later phases, but washout is not consistently reported as a typical feature across studies. Prominent vascular supply and arterial phase enhancement of an adjacent hepatic vein are often seen. Hepatobiliary phase hypointensity is expected. Atypical features include calcifications and cystic degeneration. Although presence of fat is helpful, it is nonspecific, as hepatocellular carcinoma (HCC) and adenoma may also contain fat. HAML is frequently misdiagnosed on imaging as HCC, other hepatic neoplasms, or metastases — in over 90% of cases in one study. Helpful features for diagnosis of HAML over HCC include nondiseased liver, marked arterial phase hyperenhancement (>120 HU), peripherally decreasing enhancement rim, absence of tumor capsule, early draining vein, and lack of diffusion restriction. Biopsy provides diagnostic confirmation, although pathologic misdiagnosis may occur.
When a confident diagnosis of HAML is established, surveillance with imaging is appropriate. Surgical resection can be considered in cases of inconclusive diagnosis, symptoms, or growth over time.
References
- Klompenhouwer AJ, Dwarkasing RS, Doukas M, et al. Hepatic angiomyolipoma: An international multicenter analysis on diagnosis, management, and outcome. HPB (Oxford). 2020;22(4):622-629.
- Lee SJ, Kim SY, Kim KW, et al. Hepatic angiomyolipoma versus hepatocellular carcinoma in the noncirrhotic liver on gadoxetic acid-enhanced MRI: A diagnostic challenge. AJR Am J Roentgenol. 2016;207(3):562-570.
- Lee SJ, Kim SY, Kim KW, et al. Hepatic angiomyolipoma with minimal fat, mimicking hepatocellular carcinoma. Clin Mol Hepatol. 2012;18(3):330-335.
- Du S, Li Y, Mao Y, et al. Diagnosis and treatment of hepatic angiomyolipoma. Hepatobiliary Surg Nutr. 2012;1(1):19-24.
- Jeong B, Kim SY, Kang HJ, Shin J. Hepatic angiomyolipoma presenting as a hyperintense lesion during the hepatobiliary phase of gadoxetic acid enhanced-MRI: A case report. iMRI. 2022;26:60-65.
- Klompenhouwer AJ, Verver D, Janki S, et al. Management of hepatic angiomyolipoma: A systematic review. Liver Int. 2017;37(9):1272-1280.
- Cai PQ, Wu YP, Xie CM, Zhang WD, Han R, Wu PH. Hepatic angiomyolipoma: CT and MR imaging findings with clinical-pathologic comparison. Abdom Imaging. 2013;38(3):482-489.
- Chernyak V, Fowler KJ, Kamaya A, et al. Liver Imaging Reporting and Data System (LI-RADS) Version 2018: Imaging of hepatocellular carcinoma in at-risk patients. Radiology. 2018;289(3):816-830.
