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