Prognostic Significance of Lateral Lymph Node Micrometastases in Lower Rectal Cancer

PURPOSE: The aims of this study were to determine the rate of lymph node micrometastases and to evaluate their prognostic value in lateral lymph nodes in lower rectal cancer at or below the peritoneal reflection. METHODS: A retrospective analysis was made of 892 lymph nodes from 66 consecutive patients who had undergone radical resection with lateral lymph node dissection. These lymph nodes were examined immunohistochemically with an antibody against cytokeratins 7 and 8, CAM5.2. RESULTS: Routine hematoxylin-eosin staining revealed 9 patients with positive lateral lymph nodes that were stained consistently with CAM5.2. Among 57 patients in whom lateral lymph node metastases were not detected by hematoxylin-eosin staining, cytokeratin staining was positive in 19 nodes (2.7 percent) from 11 patients (19.3 percent). These 11 patients with micrometastases in lateral nodes showed a significantly high recurrence rate (P = 0.048) and worse overall survival (P = 0.01) than the 46 patients without lateral node metastases. The recurrence rate and overall survival of patients with micrometastases did not differ significantly from those of patients with positive lateral nodes with hematoxylin-eosin staining. Local recurrence developed in 6 of 66 patients, but neither the presence nor the absence of micrometastases in lateral nodes influenced the local recurrence rate. CONCLUSION: The presence of nodal micrometastases leads to a poor prognosis. The survival of patients with micrometastases was not different from that of patients with overt metastases. Therefore, patients with cytokeratin-positive cells in lateral lymph nodes should be regarded as having overt metastases.