Potential causes of stage migration and their prognostic implications in colon cancer: a nationwide survey of specialist institutions in Japan.

OBJECTIVE The actual status of stage migration in colon cancer that occurs in the procedure of preparing pathological specimens of lymph nodes has not been fully investigated. METHODS A nationwide survey of specialist institutions for colon cancer treatment was conducted to clarify interinstitutional differences in processing surgical specimens. After categorizing 111 institutions on the basis of their practice of processing specimens, distribution of tumor stage and the recurrence status of 3294 colon cancer patients treated with the same level of lymphadenectomy were compared. RESULTS Patients were diagnosed with lower tumor stages in non-teaching hospitals, in hospitals where lymph nodes were retrieved by less experienced clinicians and in hospitals in which lymph nodes were retrieved with procedures that preserved the planes of surgery around the primary tumor. However, the process of sectioning and embedding lymph nodes did not affect stage distribution. The average number of lymph nodes examined per case in each institute was 19.4. Institutional number of lymph nodes examined was not associated with node positivity but it did affect the substage in Stage III for number of lymph nodes examined ≥21. In contrast, none of the factors associated with stage migration caused interinstitutional differences in the recurrence status according to the tumor stage. CONCLUSIONS Considerable variety in the processing of surgical specimens existed even within one country, which could be a cause of stage migration in colon cancer. Better awareness of the clinical impact of the lymph node retrieval process is needed; an international guideline to standardize the treatment of surgical specimens might increase the value of tumor staging.