BACKGROUNDTo analyze clinicopathological correlation of detection of lung cancer micrometastasis in regional lymph nodes (LNs) by reverse transcriptase-polymerase chain reaction (RT-PCR).

METHODSRegional LNs (n=261) were obtained from 40 patients with lung cancer who underwent lobectomy. Each LN was bisected. Half of each LN was subjected to histological examination (HE) and the other half was subjected to RT-PCR amplification of CK19 mRNA.

RESULTSIn 18 of 40 patients, the metastasis in regional LNs was found by both HE and RT-PCR. Of 22 N0 diseases diagnosed by HE, 6 (27%) were found to express CK19 mRNA in regional LNs. According to the results of regional LNs metastasis in 40 patients by CK19 RT-PCR, the presence of the CK19 product in LNs was related to tumor size (Chi-square=5.76, P < 0.025), the presence of tumor vascular invasion (Chi-square=3.88, P < 0.05), cell differentiation of the tumor (Chi-square=7.08, P < 0.01) and P-TNM stages (Chi-square=7.42, P < 0.01). In the histologically node-negative patients, lymph node micrometastasis was significantly related to tumor size (P=0.038, exact test) and P-TNM stage (P=0.01, exact test). However, the results of routine histological examination did not show the above clinicopathological correlation (P > 0.05).

CONCLUSIONSThe RT-PCR method is superior to routine histological examination in detecting metastasis in LNs. The micrometastasis in LNs can be detected accurately by RT-PCR. It is helpful for screening the patients in whom the early subclinical metastasis exists and disclosing the intrinsic rule of malignancy metastasis.