The impact of the largest metastasis size on nodal tumor burden in colorectal carcinomas: implications for the sentinel lymph node theory in cancers of the large intestine

BACKGROUND AND OBJECTIVES: Successful sentinel lymph node (SLN) biopsy has been reported in colorectal cancer (CRC), but its results are still controversial. The SLN theory suggests that there is an orderly spread from the primary tumor to the SLNs first, and from the SLNs to further nodes later. This study examines the influence of nodal metastasis size on further nodal involvement. METHODS: CRC resection specimens with nodal metastasis have been evaluated for the maximum nodal metastasis size for a period of 5 years. All lymph nodes (LNs) were submitted to standard histological examination. RESULTS: Two hundred thirty-five CRC specimens with a single invasive tumor were assessed. The mean numbers of LNs examined and involved were 18 and 4, respectively. The largest metastasis size ranged from 0.14 to 22.1 mm. There was a significant correlation between this parameter and the number or the ratio of LNs involved (Spearman's Rho: 0.517, and 0.382, respectively; P <0.0001). A cluster analysis identified three relatively distinct groups of low, intermediate, and extensive nodal involvement. CONCLUSIONS: The correlation of the largest metastasis size with the number and the ratio of involved nodes may be an indirect proof of the sequential spread from first echelon LNs to further nodes. However, the data suggest a more complex process: with increasing metastasis size, the number of involved nodes and its variability increase more than might be expected. This suggests a recruitment or cascade process, which becomes more unpredictable as nodal tumor burden increases.