The impact of immunohistochemical detection of positive lymph nodes in early stage lung cancer

Background: Detection of micrometastatic disease is an interesting area in non-small cell lung cancer (NSCLC). We conducted a study to determine whether the detection of mediastinal lymph node spread by immunohistochemical (IHC) analysis offers some prognosis with respect to patients' disease-free survival or not. Methods: Between 1997 and 2003, twenty-one early stage lung cancer patients underwent complete resection with mediastinoscopy and systemic nodal dissection. Four hundred and twenty-six paraffin-embedded lymph node sections from 21 patients were analyzed. Epithelial specific-antigen Ab-9 and Keratin-Pan Ab-1 were used as IHC marker. Results: Based on nodal spread four of the 21 patients (19.04%) were up-staged after IHC analysis. Two patients with stage IB (T2N0) up-staged to stage IIIA (T2N2); two patients staged as IIB (T2N1) up-staged to IIIA (T2N2). Statistical analysis showed that the lymphatic dissemination detected with IHC analysis was associated with reduced disease-free survival (DFS) (p = 0.002). Conclusions: Our study provides some indication that patients with lymphatic micrometastasis have a reduced DFS. Before creating a new TNM staging system, more information is needed to understand the prognostic impact of micrometastatic dissemination.