Prognostic relevance of immunohistochemically detected lymph node micrometastasis in patients with gastric carcinoma

BACKGROUND: Micrometastases consisting of one to a few cells in lymph nodes resected during gastrectomy are difficult to identify using conventional hematoxylin and eosin (H&E) stains. It has been shown that immunostaining for cytokeratins is effective in detecting lymph node micrometastasis in a variety of human tumors, but only a few previous reports demonstrated its use in the treatment of patients with early and advanced gastric carcinoma, and those reports had conflicting results. METHODS: In this study, 3625 regional lymph nodes that were dissected in gastrectomy specimens from 153 patients with early-stage gastric carcinoma (46 patients) and advanced gastric carcinoma (107 patients) were immunostained with the anticytokeratin cocktail AE1/3 for micrometastasis (median, 23 lymph nodes; range, 8-66 lymph nodes). Micrometastasis (MM) was defined as a single tumor cell or clusters of tumor cells that were missed on conventional examination with H&E stains but were detected by immunostaining with broad-spectrum anticytokeratin antibodies. RESULTS: Lymph node metastasis (LNM) was detected in 609 lymph nodes (17%) by H&E staining. MM was identified in another 191 of the remaining lymph nodes (6.3%) from 75 patients. Twenty-eight of those patients were up-staged. There was a significant correlation between MM and depth of tumor invasion (P < 0.01). Patients with MM had a decreased 5-year survival rate (49%) compared with patients without MM (76%) for both early and advanced gastric carcinoma. The effect of MM on survival was most pronounced for patients in the Stage I and LNM negative group. CONCLUSIONS: Immunohistochemical examination using broad-spectrum anticytokeratin antibodies increased the detection rate of LNM and had a significant impact on staging and survival in patients with gastric carcinoma.