[Clinicopathological study on nodal molecular staging of non-small-cell lung cancer]

To investigate the practicability of detecting the micrometastasis in lymph nodes of no-small-cell lung cancer (NSCLC) by means of reverse transcriptase-polymerase chain reaction (RT-PCR).

Regional lymph node samples were collected during operation from 25 patients with NSCLC randomly selected. The lymph node sample from each patient was divided into 2 groups: lymph nodes of hilum of lung and of mediastinum. Every lymph node was divided into two parts of the same size. One half part of the lymph node was examined by hematoxylin eosin (H&E) staining. If HE staining discovered metastasis, further examination was not needed. If HE staining failed to discover metastasis, then all the remaining lymph node samples of each patient were mixed together to undergo RT-PCR for cytokeratin 19 (CK(19)), a tissue marker of epithelium and epithelial tumors.

(1) 195 lymph nodes from 25 patients with NSCLC were examined by H&E staining. 30 lymph nodes in 9 patients showed gross nodal metastasis and none showed micrometastatic tumor cells. (2) Of the 39 groups of mixed regional lymph node samples which were diagnosed to be devoid of metastases by H&E staining, 11 groups were found to have positive reactions to CK(19) mRNA. (3) Six of the sixteen patients staged as PN(0) had hilum lymph nodal micrometastasis, while 5 of nine patients with stage PN(1) had mediastinal lymph nodal micrometastasis (chi(2) = 54.063, P = 0.0043).

(1) H&E staining can accurately detect gross nodal metastasis in the lymph nodes of the patients with NSCLC, but is unfit for detecting lymph nodal micrometastasis. (2) RT-PCR can facilitate the detection of occult micrometastatic tumor cells in the lymph nodes of NSCLC, and its assessment of nodal micrometastasis can provide a refinement of molecular stage for partial patients with stage I to II.