Comparative study on molecular staging of lymph nodes in non-small cell lung cancer patients

Objective: The postoperative survival of patients with non-small cell lung cancer (NSCLC) is mainly determined by clinical pathologic stage. However, recurrence is not rare in stage I NSCLC patients. This study was to explore whether conventional pathologic stages of some NSCLC were underestimated.

Methods: A total of 195 lymph nodes were taken from 25 NSCLC patients during operation. Each lymph node was cut into two parts equally: one part was subjected to hematoxylin-eosin (HE) and immunohistochemical (IHC) staining; the other part of the lymph nodes in the same region in a given patient was mixed for reverse transcription-polymerase chain reaction (RT-PCR).

Results: With HE staining, 30 of the 195 lymph nodes showed gross nodal metastasis, and none showed micrometastasis. IHC staining was performed on 135 lymph nodes that were identified as free of metastasis by HE staining, 31 showed micrometastasis; none showed gross nodal metastasis. Of 39 groups of mixed regional lymph nodes which were diagnosed to be free of metastasis by HE staining, 11 groups were found to be positive by RT-PCR. There was a correlation between IHC staining and RT-PCR for detection of nodal micrometastasis of NSCLC (U=7.682, P<0.001).

Conclusions: HE staining can accurately detect gross nodal metastasis in NSCLC patients, but is unfit for detecting nodal micrometastasis. IHC staining can improve the detection rate of occult nodal micrometastasis. RT-PCR has similar value to IHC staining in detecting nodal micrometastasis.