A Case Report of Encapsulated Hepatic Angiomyolipoma without Fat Component

Abstract

A 37-year-old woman was admitted to our hospital because of upper abdominal pain. Ultrasonography in a routine medical check-up showed a liver tumor. Abdominal computed tomography (CT) showed a low density mass in the caudate segment of the liver (S1). Abdominal CT with contrast enhancement (CE) revealed a high density area 7.0 cm in diameter at the arterial phase, and the area was washed out at the late phase. Abdominal magnetic resonance imaging showed a low intensity mass on the T1-weighted image, a slightly high intensity mass on the T2-weighted image, and no signal decrease at the opposed-phase T1-weighted image. No fat component was identified. We could not completely rule out a possibility of hepatocellular carcinoma and performed left lobe hepatectomy. Macroscopically the tumor was solid 6.5×5.5×6.0 cm in size, and was encapsulated. Histopathologically the tumor was composed of only smooth muscles, but lipocytes were not included and the tumor had been encircled by a fibrous capsule. Smooth muscle cells consisting of major component of the tumor were positive for HMB-45 and α-SMA on immunohistochemical staining. Hepatic angiomyolipoma was finally diagnosed.