Hepatic angiomyolipoma: differential diagnosis from other liver tumors in a special reference to vascular imaging - importance of early drainage vein

Abstract

A 51-year-old female had been diagnosed with a hemangioma in the hepatic segment 6 (S6). After a 6-year follow-up, enlargement of the tumor was detected. The tumor was clearly enhanced in the arterial phase, and the enhancement remained in the portal phase on computed tomography (CT). Although the primary differential diagnosis on CT was hepatocellular carcinoma (HCC), we worried about the possibility of other vessel system tumors because the tumor remained to be enhanced at the portal phase for HCC and all tumor markers of HCC were negative. We performed angiography to determine the tumor nature and to seek other tumors. Angiography showed tumor stain at the hepatic S6 with an early obvious drainage vein from the tumor flowing through the right hepatic vein into the inferior vena cava. In addition to tumor stain and the drainage vein, there were many small poolings of contrast medium in the whole liver, which were suspected as dilatation of the hepatic peripheral artery. We suspected the tumor as a benign tumor such as hepatocellular adenoma or focal nodular hyperplasia, but the possibility of HCC could not be ruled out. Hepatic posterior sectionectomy was done to completely remove the drainage vein with the tumor. Intraoperative histological examination revealed the tumor as not malignant and not HCC. Later, immunohistochemical analysis uncovered that the tumor had high expression of HMB-45 and, therefore, the final diagnosis was angiomyolipoma. We think that detecting an early drainage vein from the tumor would be a key point for diagnosing hepatic angiomyolipoma.

Keywords: Angiography; Angiomyolipoma; Early drainage vein; Hepatocellular carcinoma; Liver.

Figure 1

Computed tomography (CT) imaging of the abdomen. A. There is a tumor at the segment 6 of the liver, which is well enhanced by contrast medium at the arterial phase (arrow). B. The tumor remains to be enhanced by contrast medium in portal phase (arrow).

Figure 2

Magnetic resonance imaging (MRI). A. In-phase image of chemical shift T1-weighted MRI shows low intensity at the tumor of segment 6 (arrow). B. No further decrease of signal intensity was observed in out-of-phase image (arrow). C. T2-weighted MRI shows high intensity (arrow). D. Diffusion-weighted imaging showed high intensity at the tumor (arrow).

Figure 3

Digital subtraction angiography (DSA) and reconstructed image of computed tomography during angiography. A. Angiography shows a tumor stain (arrow) at the hepatic segment 6 with bold feeding artery. An early drainage vein from the tumor is detected at hepatic arterial phase. B. Blood flow of drainage vein is gradually clear (arrow). C. Contrast medium flows intensely into inferior vena cava (arrows). There were many small poolings of enhanced medium, which are suspected as peripheral blood dilatation, around the whole liver. D. Three dimension reconstructed image of computed tomography during arterial angiography. There is an efferent vessel from the tumor (arrow).

Figure 4

Gross and histological findings. A. The resected fresh specimen showed dark yellowish soft tumor, measuring 31 mm in diameter, with no capsule, and a small amount bleeding on the cutting surface. A neighboring small mass of 6.5 mm in diameter existed (arrow). B. Histological examination revealed that the tumor showed that there were many epithelioid myoid cells, epithelioid clear cells with sinusoidal vessels, and mature adipose tissues (H & E staining, objective; ×40). C. Immunohistochemical analysis revealed that epithelioid myoid cells showed high expression of HMB-45 (objective; ×40). D. Many capillaries positive for CD34 antigen had grown (objective; ×20). E. The Ki67 index was 0.3% (objective; ×40). F. The tumor cells were negative for c-kit (CD117), and only plasma cells were positive (objective; ×20). G. Expression of TSC1/hamartin reduced in comparison with surrounding liver tissue (tumor; left lower, normal liver; right upper, objective; ×20). H. Elastica-Masson stain. Tumor infiltrated into hepatic veins (objective; ×4).