NX      Nodes cannot be measured
N0       No involved lymph nodes
N1       Single involved node,  same side,  less than 3cm(1 1/4in.)
N2       Single involved node,  same side,
           N2a    one node,  3-6cm(1 1/4-2 1/2in.)
           N2b    multiple nodes,  none over 6cm(2 1/2in.)
N3       Massive involved lymph nodes
           N3a    a node over 6cm(2 1/2in.) on same side
           N3b    nodes on both sides
           N3c    nodes only on opposite side