Additional lymph node examination from entire submission of residual mesenteric tissue in colorectal cancer specimens may not add clinical and pathologic relevance

The examination of lymph nodes in colorectal cancer is a critical procedure for determining the stage, which determines prognosis and need for adjuvant therapy. The current recommendation is to harvest at least 12 lymph nodes by conventional manual node dissection (MND). Recent studies have suggested that all lymph nodes in mesenteric tissue should be retrieved using a special method such as the entire submission of residual mesenteric tissue (ESMT) after MND. We investigated the efficacy of ESMT with its potential impact on the pN stage. After an MND in 48 consecutive colorectal cancer resection specimens, the residual mesenteric tissues were entirely submitted for routine histologic examination by ESMT. After initial MND, 933 (mean, 19.4) lymph nodes were found, and there were 29 pN0, 10 pN1, and 9 pN2 cases. By ESMT after MND, 1132 (mean, 23.6) additional lymph nodes were found. Most (88.6%) of them were 2.0 mm or less in maximum dimension, and of the 1132 additional lymph nodes, 14 (1.2%) lymph nodes revealed tumor metastases. Although there was no additional nodal metastasis in any of the initial 29 pN0 cases, additional nodal metastases were found in 10 of the original 19 node-positive cases. Two of the 10 cases with additional positive nodes identified would be upstaged from pN1 to pN2. Both of these cases had fewer than 12 nodes identified by MND but had 1 and 2 additional nodes identified by ESMT. Our study demonstrated that MND seems to be accurate and efficient in evaluating tumors with pN stage of pN0. Although ESMT may be useful to assess the correct pN stage in pN1 cases with fewer than 12 lymph nodes in MND, it may not add any additional information in pN0 cases or in node-positive cases with 12 or more lymph nodes found by MND.