Clinical Significance of Immunohistochemically Detecting Positive Expression of Cytokeratin in Lymph Nodes of Patients with Stage I Non-Small Cell Lung Cancer

Objective To detect the positive expression of Cytokeratin (CK) in lymph nodes of patients with stage I non-small cell lung cancer (NSCLC) to confirm the presence of micrometastasis and to study the correlation with recurrence, metastases and prognosis. Methods A total of 246 hilar and mediastinal lymph nodes indicated to be tumor cells free by conventional histopathologic methods were removed during surgery from 33 patients with completely resected stage I NSCLC. The lymph ndoes were analyzed for micrometastasis by Streptavidin Biotin-Peroxidase Complex(SABC) technology using CK as a micrometastatic marker. Results CK-positive cells were detected in 12 (4.9%) of 246 lymph nodes, in 10 (30.3%) of 33 patients. There was significant difference between the recurrence and metastases rate of patients with or without positive expression of CK(80.0% vs. 26.1%,χ2=7.015,P=0.016).The median survival period of patients with positive expression of CK was significantly shorter than those with negative expression of CK(21months vs. 60months, P=0.016).The patients with positive expression of CK in the lymph nodes had a poor prognosis by both univariate (P=0.004) and multivariate analyses (P=0.004). Conclusions Immunohistochemical stain for CK is a valid method for detecting and assessing micrometastasis in lymph nodes of lung cancer patients. The detection of lymph nodal micrometastatic tumor cells by immunohistochemistry using CK provides an accurate assessment of tumor staging and has powerful prognostic implications for completely resected stage I NSCLC patients and provides theoretical evidence for synthetic therapy of stage I NSCLC patients.