Ultrastaging of sentinel lymph nodes (SLNs) vs. non-SLNs in colorectal cancer-do we need both?

Background: The aim of this study to analyze whether ultrastaging of initially negative nonsentinel lymph nodes (non-SLNs) would increase nodal positivity in colon cancer and rectal cancer. Methods: After SLN mapping (SLNM), SLNs were ultrastaged by 4 hematoxylin and eosin and 1 immunohistochemistry sections. A blinded pathologist reexamined initially negative non-SLNs by 3 additional hematoxylin and eosin and 1 immunohistochemistry sections. Results: In 156 colon cancer and 44 rectal cancer patients, 2,755 nodes were identified (494 SLNs and 2,261 non-SLNs). Metastases were detected in 20.9% of SLNs and 8.6% of non-SLNs (P < .0001). After ultrastaging non-SLNs, only .58% became positive for metastases in 12 patients. Of these, 10 already had positive lymph nodes, hence no change of staging occurred. Ultrastaging upstaged only 2 of 200 patients (1%). Conclusions: The chance of finding additional metastases by ultrastaging of all non-SLNs is extremely low (<1%) and of little benefit.