Hepatic Angiomyolipoma

Abstract

Introduction: Comprehensive analysis is essential in determining the appropriate etiology of clinical manifestations. Pathological analysis and immunohistochemistry can differentiate hepatic angiomyolipoma (AML), a rare yet benign tumor, from other more common liver lesions. Case Description: A 62-year-old male with human immunodeficiency virus and Hepatitis B presented with epigastric pain, nausea, and a 30 pound weight loss over 6 months. Physical examination was significant for mild epigastric and right upper quadrant tenderness. Computed tomography (CT) of the abdomen and pelvis revealed a large, well defined heterogeneous mass of the right hepatic lobe measuring 9.6cm in maximal diameter, with vascular soft tissue intermixed with macroscopic fat. Radiologic differentials included a primary hepatic neoplasm such as hepatocellular carcinoma or hepatic AML. Magnetic resonance imaging (MRI) of the liver with triple phase contrast was performed and the lesion remained suspicious for hepatocellular carcinoma. AFP was 3.7 (normal <8.5 ng/mL). A percutaneous CT-guided biopsy of the mass was performed. Histology showed large cells with eosinophilic and fibrillar cytoplasm, admixed with adipocytes, inflammatory cells and extramedullary hematopoiesis consistent with a hepatic AML. This was confirmed with positive staining for smooth muscle actin, Melan-A and HMB-45. Given the size of the AML and the symptoms, the patient underwent open excision of the mass with partial right hepatic lobectomy. Intraoperatively, the lesion was found to be encapsulated. The resected mass was 9.3 x 7.4 x 4.3cm in size and histology confirmed the initial biopsy findings. There were no postoperative complications and he remained symptom free at his follow-up appointment.Figure 1Figure 2Figure 3Discussion: Hepatic AML is a benign mesenchymal tumor composed of variable proportions of smooth muscle cells, adipocytes, and blood vessels. It is most often a solitary tumor found incidentally, although a minority present with upper abdominal discomfort related to mass effect. MRI is considered to be the imaging study of choice but has been reported to misdiagnose between 48-90% of cases given variability in tumor composition. They can be mistaken for hepatocellular carcinoma, hemangioma or hepatic adenoma. Definitive diagnosis is dependent on tissue histopathology and immunostaining for muscle-specific markers such as smooth muscle actin as well as melanoma markers HMB-45 and melan-A.