Accurate lymph-node detection in colorectal specimens resected for cancer is of prognostic significance

Lymph-node involvement is the most important prognostic factor in colorectal cancers. Many staging systems adopted node status as a parameter of tumor classification. However, the number of identified and positive glands varies across articles, depending on specimen examination. There is a consistent risk of substaging tumors and undertreating patients. Aim of this study was to investigate the prognostic significance of different pathologic methods.

Eight hundred one patients who underwent curative resection of colorectal cancer entered the study and were divided into two groups. In Group 1 the specimen was "en bloc" fixed, and nodes were identified by sight and palpation. In Group 2 the mesentery of the excised specimen was dissected away from the bowel, stretched, and pinned to cork board. The mesenteric segment surrounding the origin of principal vessels was divided from the segment surrounding the colic vessels. All specimen segments were fixed, node identification being performed by sight and palpation. Examined and positive nodes were recorded, and metastatic rate and incidence was calculated in the two groups. Patients were classified with use of different staging systems. Survival rates were calculated, related to tumor stage, and compared statistically. Pathologic procedures were included in a multivariate analysis.

A significantly higher number of detected and positive nodes and metastatic rate (37.5 vs. 30.2 percent; P < 0.05) were observed in Group 2; 45.2 percent of Group 2 and 25.3 percent of Group 1 cases had more than three positive nodes (P < 0.05). In Group 2 several patients shifted from earlier to more advanced stages compared with Group 1 cases. Five-year and ten-year survival rates were significantly higher (P = 0.04) in Group 2 (81.5 and 77.2 percent) than in Group 1 (76.7 and 61.5 percent), mostly in patients with TNM Stage N0. Survival analysis related to Astler and Coller's and Tang's classifications confirmed such features. Higher rates of local recurrences and distant metastases were found in Group 1, particularly if related to node status (P < 0.05). Multivariate analysis demonstrated the pathologic method is an independent prognostic factor.

This study demonstrates the prognostic impact of specimen examination. Inaccurate methods could down-stage the tumor and exclude the patient from adjuvant therapies, with detrimental effects on the outcome of the case.