The clinical significance of lymph node size in colon cancer

To date, the clinical value of lymph node size in colon cancer has been investigated only in a few studies. Only in radiological diagnosis is lymph node size routinely recognized, and nodes >= 10mm in diameter are considered pathologic. However, the few studies regarding this topic suggest that lymph node size is not a reliable indicator of metastatic disease. Moreover, we hypothesized that increasing lymph node size is associated with favorable outcome. By performing a morphometric study, we investigated the clinical significance of lymph node size in colon cancer in terms of metastatic disease and prognosis. A cohort of 237 cases with excellent lymph node harvest (mean lymph node count: 33 +/- 17) was used. The size distribution in node-positive and -negative cases was almost identical. In all, 151 out of the 305 metastases detected (49.5%) were found in lymph nodes with diameters <= 5mm. Only 25% of lymph nodes >10mm showed metastases. Minute lymph nodes <= 1mm were involved only very rarely (2 of 81 cases). In 67% of the cases, the largest positive lymph node was <10mm. The prognostic relevance of lymph node size was investigated in a subset of 115 stage I/II cases. The occurrence of >= 7 lymph nodes that were > 5mm in diameter was significantly associated with better overall survival. Our data show that lymph node size is not a suitable factor for preoperative lymph node staging. Minute lymph nodes have virtually no role in correct histopathological lymph node staging. Finally, large lymph nodes in stage I/II disease might indicate a favorable outcome. Modern Pathology (2012) 25, 1413-1422; doi: 10.1038/modpathol.2012.92; published online 8 June 2012