The correlation between detection of occult neo-plastic cells (ONCs) in lymph node sinuses and the recurrence/metastasis of primary breast, lung, esophageal, and gastric cancer was examined. Among patients with Stage I-III cancer treated by radical resection with dissection of at least 10 lymph nodes, 40 patients who suffered recurrence/metastasis within 5 years post-operatively and 94 patients who did not have recurrence within 5 years were randomly selected. A total of 1,340 lymph nodes were subjected to immunohistochemical staining for cytokeratin to identify ONCs. Then the sensitivity, specificity, positive predictive value, and negative predictive value of ONCs were determined for predicting the recurrence of each cancer. These parameters were respectively 40.0, 75.9, 62.4, and 55.8% for breast cancer, while the respective values were 50.0, 77.4, 68.9, and 60.8% for lung, 57.1, 64.3, 61.5, and 60.0% for esophageal, and 68.8, 65.0, 66.3, and 67.5% for gastric cancer. All of the parameters exceeded 65% for gastric cancer. ONCs also showed a high specificity for breast and lung cancer, but both the sensitivity and specificity were low for esophageal cancer.