Methionyl-tRNA Synthetase is a Useful Diagnostic Marker for Lymph Node Metastasis in Non-Small Cell Lung Cancer

Abstract

Purpose: Identification of lymph node (LN) metastasis in non-small cell lung cancer (NSCLC) is critical for disease staging and selectionof therapeutic modalities. Sometimes it is not possible to obtain LN core tissue by endobronchial ultrasound-guided transbronchialneedle aspirate (EBUS-TBNA), resulting in low diagnostic yield. Materials and Methods: In this study, 138 specimens were collected from 108 patients who underwent EBUS-TBNA under thesuspicion of LN metastasis of NSCLC. Diagnostic yields of anti-CD45 and anti-methionyl-tRNA synthetase (MRS), immunofluorescent(IF) staining on cytology specimens were compared with those of conventional cytology and positron emission tomography-computed tomography (PET-CT). Results: MRS was strongly expressed in NSCLC cells metastasized to LNs, but weakly expressed in cells at the periphery of the LNgerminal center. The majority of cells were CD20 positive, although a few cells were either CD3 or CD14 positive, indicating thatCD45 staining is required for discrimination of non-malignant LN constituent cells from NSCLC cells. When the diagnostic efficacyof MRS/CD45 IF staining was evaluated using 138 LN cellular aspirates from 108 patients through EBUS-TBNA, the sensitivity was76.7% and specificity was 90.8%, whereas those of conventional cytology test were 71.8% and 100.0%, respectively. Combining theresults of conventional cytology testing and those of PET-CT showed a sensitivity and specificity of 71.6% and 100%, and the additionof MRS/CD45 dual IF data to this combination increased sensitivity and specificity to 85.1% and 97.8%, respectively. Conclusion: MRS/CD45 dual IF staining showed good diagnostic performance and may be a good tool complementing conventionalcytology test for determining LN metastasis of NSCLC.