An angiomyolipoma is a rare benign mesenchymal tumor composed of a mixture of smooth muscle cells, blood vessels and a variable amount of fat. The appearance of an angiomyolipoma has often been reported in the kidney but rarely in the liver. The first hepatic angiomyolipoma was described by Ishak in 1976 [¹]. It can be found in both men and women, most commonly in adult women. The majority of patients with hepatic angiomyolipoma are asymptomatic. Others suffer from abdominal pain and mild fever [²]. There is no histological difference between an angiomyolipoma of the liver or the kidney. A differentiation of malignant liver tumors is often very difficult because of the high variability of the fat proportion.

Hepatic angiomyolipoma has been considered as a benign disease in the past. However, spontaneous tumor rupture, malignant transformation and recurrence after primary resection, as well as concurrent hepatic angiomyolipoma and hepatocellular carcinoma, have been reported [³,⁴]. Surgical resection should be considered for all symptomatic patients. Conservative management with close follow-up is suggested in patients with asymptomatic tumors, good compliance and absence of hepatitis virus infection, as well as small hepatic angiomyolipoma (< 5 cm) that are diagnosed through fine-needle aspiration biopsy [⁵].

Because of the variable amount of adipose tissue in hepatic angiomyolipoma, it is sometimes difficult to distinguish between benign and malignant tumors. It is possible to misdiagnose hepatic angiomyolipoma as lipoma, hepatocellular adenoma or carcinoma, sarcoma or metastasis before surgery. Contrast-enhanced spiral computed tomography shows a marked enhancement in the arterial and the portal venous phase of the soft tissue components [⁵]. Recently, CEUS has been shown to demonstrate typical imaging characteristics of hepatic angiomyolipoma; an inhomogeneous hyperenhancing pattern in arterial phase, prolonged hyperenhancing during portal and late phase, with a smooth and well-defined margin [⁶]. MRI is considered the best imaging method to identify an angiomyolipoma. It shows a hyperintensity on T2-weighted images and a hypointensity on T1-weighted images, according to the amount of adipose tissue [⁵].

Although the combination of various imaging modalities increases preoperative diagnostic accuracy it is reported to be less than 25% [⁷]. A definitive diagnosis is only given by a histological examination after surgery. Identification of smooth muscle cells, blood vessels and adipose tissue with a positive immunohistochemical reaction for HMB-45 is the final evidence for an angiomyolipoma [⁸].

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

The authors declare that they have no competing interests.

SK and OE wrote the manuscript. CL was the physician who performed CEUS. JG was the radiologist in charge of the MRI. RMS gave final approval. All authors read and approved the final manuscript.