OBJECTIVETo investigate the practicability of detecting the micrometastases in lymph nodes of no-small-cell lung cancer (NSCLC) by means of the immunohistochemical (IHC) staining.

METHODSThe lymph node samples were taken from the patients with NSCLC during the operations. Firstly, each resulting tissue block was processed for routine paraffin embedding. Then the 6 approximately 10 serial sections were chosen, each 5 microm thick, from every paraffin block of the lymph node. Finally, the first and the second last sections of each lymph node were stained by hematoxylin eosin (HE), and the other serial sections were used for the IHC staining examination with the monoclonal antibody against cytokeratin 19.

RESULTSThe paraffin embedded sections of 195 regional lymph nodes from 25 patients with NSCLC were examined by HE staining. Thirty lymph nodes in 9 patients revealed gross nodal metastases, and none of lymph node in 25 patients showed micrometastatic tumor cells. Frozen tissue sections from 135 regional lymph nodes that were staged as free of metastases by HE staining were screened by IHC staining. Thirty-one lymph nodes in 9 patients showed micrometastatic tumor cells. Five of sixteen patients staged as PN(0) had hilum lymph nodal micrometastases, versus four of nine patients with stage PN(1) had mediastinal lymph nodal micrometastases. There was a significant difference between two groups (chi(2)=52.900, P=0.0193).

CONCLUSIONSConventional HE staining can accurately detect gross nodal metastases in the lymph nodes of patients with NSCLC, but is unfit for detecting lymph nodal micrometastases. IHC staining analysis can significantly facilitate the detection of occult micrometastatic tumor cells in lymph nodes of NSCLC, and its assessment of nodal micrometastases can provide a refinement of TNM stage for partial patients with stage I to II NSCLC.