Prognostic significance of perirectal lymph node micrometastases in Dukes' B rectal carcinoma: an immunohistochemical study by CAM5.2.

Lymph node metastasis is an important prognostic factor for rectal carcinoma, but only a few attempts at defining the relationship between lymph node micrometastases and prognosis have been made. The purpose of this study was to examine the correlation between the presence of micrometastases and prognosis in patients with rectal carcinoma. Six hundred forty-four lymph nodes were dissected from 42 patients with Dukes' B rectal carcinoma and stained immunohistochemically using a monoclonal antibody, CAM5.2, that binds cytokeratin. Clinicopathological factors, rate of recurrence, and prognosis were compared among patients with and without micrometastases. Micrometastases were detected in 19 lymph nodes (19 of 644 = 2.9%) from 9 patients (9 of 42 = 21.4%). The presence of micrometastases was not related to clinicopathological factors. There were significant differences in recurrence rates (5 of 9 versus 5 of 33, P = 0.02), relapse-free survival rates (P = 0.04), and 10-year survival rates (P = 0.03) between patients with and without micrometastases. Immunohistochemistry successfully identified micrometastatic foci in lymph nodes missed with conventional staining methods. The existence of micrometastases influenced the prognosis in patients with Dukes' B rectal carcinoma.