A revised stratification using pT classification , margin status , and the number of lymph nodes identified produced 3 subgroups with significantly different LF risk in both cohorts : low risk ( pT2 ) , intermediate risk ( pT3 with negative margins AND 10 lymph nodes identified ) , and high risk ( pT3 with positive margins OR < 10 lymph nodes identified ) with 5-year LF rates of 8 % , 20 % , and 41 % , respectively , in the SWOG cohort and 8 % , 19 % , and 41 % , respectively , in the development cohort .