Histologic grade of metastatic lymph node and prognosis of rectal cancer

It is important to identify cases with a high risk of recurrence to improve the prognosis of colorectal cancer. In this study the difference between the histology of the primary lesion and that of the metastatic lymph node was investigated in an attempt to identify the cases with a high risk of recurrence.

One-hundred eighty-five patients with Dukes C rectal cancer who had undergone curative resection were investigated. The histologic grade of the metastatic lymph node was determined and compared with other clinicopathologic factors to determine its significance as a prognostic factor.

The histologic grade was the same between the primary lesion and the metastatic lymph node in 46.2 percent of all cases, although in the group with well-differentiated adenocarcinoma at the primary lesion the concordance was only 29.5 percent. In the group with well-differentiated adenocarcinoma at the primary lesion, the five-year survival rate was 75.3, 64, and 25 percent in the groups with well-differentiated, moderately differentiated, and poorly differentiated adenocarcinoma at the metastatic lymph node, respectively. The differences between the survival rates of well-differentiated and poorly differentiated adenocarcinoma at the metastatic lymph node were statistically significant (P < 0.05). According to multivariate analysis the histologic grade of primary lesion was the most significant prognostic factor (hazard ratio: 2.2801, P = 0.0008). However, in well-differentiated adenocarcinoma of patients with Dukes C rectal cancer at the primary lesion, the histology of metastatic lymph node was also an important prognostic factor.

It is clear that the histologic grade between the primary lesion and metastatic lymph node was frequently different, especially in the group with well-differentiated adenocarcinoma at the primary lesion. The analysis of the metastatic lymph node was considered to have additional importance for the prediction of prognosis.