Sentinel lymph node mapping in colorectal cancer

Background: Ultrastaging, by serial sectioning combined with immunohistochemical techniques, improves detection of lymph node micrometastases. Sentinel lymph node mapping and retrieval provides a representative node(s) to facilitate ultrastaging. The impact on staging of carcinoma of the colon and rectum in all series emphasizes the importance of this technique in cancer management. Now the challenge is to determine the biological relevance and prognostic implications. Methods: The electronic literature (1966 to present) on sentinel node mapping in carcinoma of the colon and rectum was reviewed. Further references were obtained by cross-referencing from key articles. Results: Lymphatic mapping appears to be readily applicable to colorectal cancer and identifies those lymph nodes most likely to harbour metastases. Sentinel node mapping carries a false-negative rate of approximately 10 per cent in larger studies, but will also potentially upstage a proportion of patients from node negative to node positive following the detection of micrometastases. The prognostic implication of these micrometastases requires further evaluation. Conclusion: Further follow-up to assess the prognostic significance of micrometastases in colorectal cancer is required before the staging benefits of sentinel node mapping can have therapeutic implications.