BACKGROUNDTo evaluate the diagnostic method of occult metastasis to mediastinal lymph nodes (MLNs) in patients with non-small cell lung cancer (NSCLC).

METHODSThe mRNA expression of mucin 1(MUC1) gene, an epithelial-tissue-specific gene, was detected in dissected mediastinal lymph nodes by RT-PCR assay. Seventy-eight MLNs which had no malignant evidence on routine histopathologic examination were assessed in 19 patients with stage pN0-1 disease. Five regional lymph nodes from 5 patients with benign pulmonary diseases and 5 MLNs proved malignant by histopathology from 5 patients with NSCLC were also studied as negative and positive control respectively.

RESULTSThe mRNA of MUC1 was not detected in any specimen of negative control group, whereas the mRNA was detected in all MLNs of positive control group. The mRNA in 6 out of 78 MLNs from 19 patients with pN0-1 disease was also detected, and occult metastasis was diagnosed.

CONCLUSIONSDetection of MUC1 mRNA expression might be helpful to diagnose occult metastasis in MLN in patients with lung cancer, and RT-PCR is superior to routine histopathologic examination in staging NSCLC.