Nodal staging of colorectal carcinomas from quantitative and qualitative aspects. Can lymphatic mapping help staging?

Retrospective data analysis was performed to determine the minimum number of lymph nodes required for the staging of colorectal carcinomas, and a prospective feasibility study was carried out to identify sentinel nodes in order to clarify whether these may predict the nodal status. From among 240 colorectal carcinoma specimens investigated between 1996 and 1998, 224 tumors were analyzed for their nodal status. Lymphatic mapping with vital patent blue dye injection into the peritumoral sub-serosal layer was performed in 25 patients. Blue nodes were identified by the pathologist in the unfixed specimen immediately after the resection of the bowel and were assessed separately. Of the 123 node-positive carcinomas, 40 had more than 3 nodes involved. The nodal positivity increased substantially when more than 6 nodes were assessed. The cumulative percentage analysis demonstrated that ideally 16 and 13 nodes should be obtained for the identification of any nodal involvement or the involvement of more than 3 nodes, respectively. Lymphatic mapping was successful in 24 patients (96%). Blue nodes were predictive of the nodal status in 19 cases (79%), and were the only sites of metastasis in 2 patients (15% of the node-positive cases). Lymphatic mapping with the vital blue dye technique does not seem to facilitate the staging of colorectal cancers, at least in our patient population with relatively large and deeply infiltrating tumors, and unless the technique is improved or other selective features of lymph nodes are found, all lymph nodes should be assessed. A minimum of 6 nodes, and an optimum of 16 nodes or more, are suggested from these series.