Hepatic Angiomyolipoma: Case Report, Literary Review with Emphasis on Imaging Performance for the Diagnosis

Angiomyolipoma is a rare mesenchymal neoplasm that is composed of: blood vessels, smooth muscle and fat cells. The kidneys are the site where they can be most commonly located, while the liver is a less common site of origin; these hepatic lesions are often discovered as an incidental finding in the search for diagnostic images for another pathology or are identified in the evaluation of non-specific symptoms. This tumor has been defined as a benign neoplasm, although it is suggested that some cases may have a malignant potential after hepatic resection. The definitive diagnosis is based on pathological findings supported by immunohistochemical staining. The cellular component of smooth muscle is the most specific for the diagnosis and, characteristically, these lesions are positive for homatropine methyl bromide 45 (HMB-45) and Melan-A. Because hepatic angiomyolipomas are rare and have several imaging characteristics that tend to be confused with other tumors due to their very similarity, it is not easy to achieve a definitive preoperative diagnosis, and more than half of patients are misdiagnosed with hepatocellular carcinoma or hepatic adenoma, which are much more common lesions. Regarding the imaging diagnosis of angiomyolipoma; the fatty component can be detected by CT and ultrasound. When the fat content is lower, the magnetic resonance images in weighted and diffusion sequences are useful due to their sensitivity. In fact, magnetic resonance using conventional sequences and weighted by diffusion have become a valuable technique for the characterization of focal solid liver lesions.