Optimized workup of lymph nodes in regard to UICC classification of colorectal carcinoma

AIMS: Treatment and outcomes in colorectal carcinoma (CRC) depend on the UICC classification, depth of invasion, and distant metastases. However, it is not clear whether an extensive workup of lymph nodes (LNs) is important for the adequate determination of metastases. Therefore, we compared the number of LNs and metastases obtained by a standard protocol (SP) and an extended protocol (EP) in two series with a total of 105 CRC cases and 2417 LNs. METHODS AND RESULTS: In the first series, the EP included complete stepwise sectioning of all LN-bearing paraffin blocks in each case, increasing the total number of LNs from 1247 in the SP to 1333 in the EP and the number of metastases from 69 to 80. One pTNM pN1a case became pN1b, and two pN1b cases became pN2a. The staging, and thus the therapy, changed in none of them. Furthermore, no relevant effect of embedding one versus both halves of large LNs >5 mm was evident. In the second series, the EP included immunohistochemical staining for pan-cytokeratin (monoclonal antibodies AE1/AE3) of all LN-bearing paraffin blocks in a given case. The number of detected metastases rose from 82 to 89, with a constant total 1084 LNs. In two cases, the pTNM classification changed from pN2a to pN2b. Staging and therapy changed in none. CONCLUSION: An extensive workup of LNs is not mandatory in patients with CRC. A straightforward protocol is sufficient to guide clinicians to the appropriate therapy.