Fig. 2

Schematic diagram of the distribution of metastatic lymph nodes in the PLV region. The blue line is the horizontal line through the anterior surface of the trapezius, which was used to calculate the vertical distance between the central points of the metastatic lymph nodes in the PLV region and the horizontal line. The light blue line is the delineation of the PLV region with the ipsilateral metastatic lymph nodes of levels Va, Vb, and Vc. The green circle indicates some metastatic lymph nodes of the PLV region that were recreated proportionally on the CT images of a standard patient to further understand the location of their distribution