Frequency and predictive factors of nodal micro-metastasis (NMM) in resectable non-small cell lung cancer.

Background: The frequency of lymph nodal micrometastasis (NMM) in resectable non-small cell lung cancer (NSCLC) is frequently underestimated when relying solely on standard hematoxylin and eosin staining during pathological examination. Methods: This is a retrospective cross-sectional diagnostic research. Medical records of resectable pN0 NSCLC patients who underwent curative resection in Maharaj Nakorn Chiang Mai Hospital between January 2006 to December 2017 were retrospectively reviewed. Immunohistochemistry (IHC) staining using cytokeratin AE1/AE3, p53 and BerEP4 markers was employed to detect NMM. Primary objective of this study was to determine frequency of NMM in pN0 resectable NSCLC. Results: This study included 98 patients with pN0 NSCLC, of which 47 were male and 51 were female. NMM was detected in 21 of 98 patients (21.43%). Lymph node station 10 and 7 were the most common site of micrometastasis among patients with N1 and N2 micrometastasis, respectively. Cytokeratin AE1/AE3 was the most sensitive antibody in detecting micrometastasis in lymph nodes, identifying 25 out of 27 positive lymph nodes. Tumor size greater than 4 cm was a statistically significant predictive factor for NMM with risk ratio 6.69 [95% confidence interval (CI): 2.38-18.85, P<0.001]. Conclusions: NMM was identified in 21.43% of pN0 resectable NSCLC patients and tumor size greater than 4 cm is predictive factor for NMM.