Background: Current methods of disease staging often fail to detect small numbers of tumor cells in lymph nodes. Metastatic relapse may arise from these few cells.
Methods: We studied 1308 lymph nodes from 68 patients with esophageal cancer without overt metastases who had undergone radical en bloc esophagectomy. A total of 399 lymph nodes obtained from 68 patients were found to be free of tumor by routine histopathological analysis and were studied further for isolated tumor cells by immunohistochemical analysis with the monoclonal anti-epithelial-cell antibody Ber-EP4. This antibody did not stain lymph nodes from 24 control patients without carcinoma.
Results: Of the 399 "tumor free" lymph nodes, 67 (17 percent), obtained from 42 of the 68 patients, contained Ber-EP4-positive tumor cells. Fifteen of 30 patients who were considered free of lymph-node metastases by histopathological analysis had such cells in their lymph nodes, and 5 of the 15 had small primary tumors. Ber-EP4-positive cells found in "tumor free" nodes were independently predictive of significantly reduced relapse-free survival (P=0.008) and overall survival (P=0.03). They predicted relapse both in patients without nodal metastases (P=0.01) and in those with regional lymph-node involvement (P=0.007). All 12 patients whose lymph nodes were negative on both histopathological and immunohistochemical analysis and who were available for follow-up survived without recurrence. The presence of micrometastatic tumor cells in bone marrow had no additional prognostic value.
Conclusions: Immunohistochemical examination of lymph nodes may improve the pathological staging of esophageal cancer.