Anechoic halo in solid liver tumors: sonographic, microangiographic, and histologic correlation.

The origin of the sonographic halo sign in liver metastases was studied after autopsy in 33 livers with macroscopic tumoral involvement. For 20 lesions a detailed comparison of findings from high-resolution 7.5- and 10-MHz sonography, microangiography, and histology was carried out. Histologic study focused on the tumor periphery and its relationship to the adjacent liver parenchyma. In particular, the type of tumor infiltration, the presence or absence of peritumoral fibrosis, and the degree of liver cell compression were assessed. In all but two cases the halo was extratumoral and was caused by peritumoral liver cell compression. In the remaining two cases the halo was tumoral and was caused by irregular fibrosis or vascularization.