Morphologic US parameters and vascular features were thoroughly evaluated and recorded on the PACS system (Marotech Inc, Seoul, South Korea) for the largest nodal lesion in each patient. Every lymph node was assessed first with gray-scale sonography for morphologic parameters in horizontal and then longitudinal sections. The short-axis diameter, long-axis diameter and diameter ratio of short to long axis (S/L ratio) were measured. Echogenicity with respect to the surrounding soft tissue was assessed and classified as hypoechoic, isoechoic, or hyperechoic. Lymph node margin was defined as regular or irregular. Echogenic hilus was distinguished between its presence or absence. Internal echo pattern was divided into heterogeneity or homogeneity. Vascular patterns were then surveyed by power Doppler sonography and categorized as the group of avascular or hilar type versus that of mixed, spotted, or peripheral type.