Pattern of lymph node micrometastasis and prognosis of patients with colorectal cancer

Studies of lymph node micrometastases in patients with colorectal cancer have ignored the prognostic significance of the number and level of lymph node micrometastases. The aim of this study was to clarify the prognostic significance of the status of lymph node micrometastases in histologically node-negative colorectal cancer. We used immunohistochemistry with anti-cytokeratin antibody CAM5.2 to examine 1013 lymph nodes in 42 patients (12 recurrent and 30 nonrecurrent) with histologically determined Dukes' B colorectal cancer. Five serial 6-microm sections were used for immunohistochemical staining. The frequency, tumor cell pattern, and number and level of lymph node micrometastases were compared between the recurrent and nonrecurrent groups. Micrometastasis was confirmed in 16% (59/373) of lymph nodes in the recurrent group and 12% (77/640) of lymph nodes in the nonrecurrent group, and the frequency of lymph node micrometastases was 92% (11/12) in the recurrent group and 70% (21/30) in the nonrecurrent group. The tumor cell pattern in the metastatic lymph nodes was similar in the recurrent and nonrecurrent groups. Micrometastasis in four or more lymph nodes occurred more frequently in the recurrent group than in the nonrecurrent group (58% vs. 20%, P < .05), and micrometastasis to N2 or higher nodes occurred more frequently in the recurrent group than in the nonrecurrent group (92% vs. 47%, P < .01). The number and level of positive micrometastatic lymph nodes was significantly correlated with postoperative recurrence of histologically determined Dukes' B colorectal cancer. This parameter is a useful prognostic indicator in histologically node-negative colorectal cancer and is helpful in planning adjuvant chemotherapy.