Potential pathological understaging of pT3 rectal cancer with less than 26 lymph nodes recovered: a prospective study based on a resampling of 50 rectal specimens.

The aim of the paper was to establish if the 12 lymph nodes recommended by tumor-node-metastasis (TNM) system are sufficient for a correct staging of rectal cancer. For this purpose, we first compared the mean number of lymph nodes recovered in the same surgical specimen at the routine sampling and at a resampling performed by a second expert gastrointestinal pathologist. The study was performed on 50 cases of pT2N0 and pT3N0 rectal cancers, with a minimum number of 12 lymph nodes recovered at first sampling, histologically negative for metastases. Resampling retrieved a variable number (1 to 24) of nodes missed at first sampling. The final pN0 status was maintained in pT2 patients, whereas in 18.7% of pT3 patients, metastatic lymph nodes were detected if the mean number of lymph nodes increased from 17.8 to 26.8 after the second sampling. Interestingly, all pN1 patients had only a single metastatic lymph node measuring less than 4.9 mm. As we have shown that most (five out of six) missed metastatic lymph nodes were detected in specimens in which a maximum number of 19 lymph nodes had been originally recovered, we strongly suggest a resampling of pT3N0 rectal specimens if less than 20 lymph nodes have been recovered.