Learning curve for endobronchial ultrasound­guided transbronchial needle aspiration: experience of a community­based teaching hospital.

Endobronchial ultrasound­guided transbronchial needle aspiration (EBUS­TBNA) is a minimally invasive procedure. This procedure is useful for nodal staging of lung cancer and evaluating mediastinal lymphoma and granuloma. The present study was a retrospective analysis of our experience when EBUS­TBNA was initially implemented. A total of 112 lymph nodes/masses (51 patients) were divided into two groups: The first and second 8 months. In the first group, 33 lymph nodes/masses (16 patients) were biopsied and tumor diagnoses were made in 9% of the cases (three lymph nodes/masses). The material was adequate to produce a cell block for microscopic analysis in 42% of cases. Subsequent tissue diagnoses were available in 50% of cases. Only one of the three malignant EBUS­TBNA diagnoses (33%) was confirmed by histological examination. In the second 8 months, 79 lymph nodes (35 patients) were sampled. Tumor/granuloma diagnoses were achieved in 27% of the cases (21 nodes) (P=0.045 versus the first 8 months) and the obtained material was adequate for producing a cell block in 90% of cases (P<0.001 versus the first 8 months). Corresponding tissue diagnoses were available in 28% of cases. Correlation of EBUS-TBNA and histological examination for tumor/granuloma diagnosis was 100% (12/12, P=0.029 versus the first 8 months). Immunostains in the cell blocks indicated that all the metastatic adenocarcinomas were thyroid transcription factor­1 (TTF­1)+ and p63­, and that all squamous cell carcinomas were TTF­1­, p63+ and cytokeratin 5/6 (CK5/6)+. Eight granulomata were identified, of which five were positive for Acid­Fast Bacilli (AFB) stain and confirmed by culture or tissue biopsy. The remaining three granulomata were AFB­negative. EGFR/KRAS mutation analysis was conducted in cell blocks of five adenocarcinomas, of which all provided sufficient diagnostic material. The findings showed a steep learning curve when EBUS­TBNA was first adopted, reflected by an increased rate of tumor/granuloma diagnoses as well as an improved sample yield for cell block preparation in the second 8 months. TTF­1, p63 and CK5/6 were useful biomarkers for distinguishing metastatic lung carcinomas.