Diagnostic yield of endoscopic ultrasound-guided fine needle aspiration cytology in lung cancer.

Summary: Introduction Endobronchial ultrasound (EBUS) guided fine needle aspiration cytology (FNAC) of mediastinal lymphadenopathy is an essential investigation in diagnosis and staging of lung cancer. EBUS FNAC can also highlight a subset of patients suitable for oncological treatments such as checkpoint inhibitors. Objectives We sought to determine the diagnostic yield rate of EBUS FNAC specimens, the range of diagnoses found and how many patients were tested for EGFR mutation, ALK1 translocation and PDL-1 expression by immunohistochemistry. Methods Eighty-four patients underwent EBUS FNAC from 1st January 2017 to 31st December 2017. Histopathological reports and additional test data from this group were analysed. Results and Discussion. Diagnostic yield was 96% with 29% of patients having a negative result. Granulomatous lymphadenopathy was identified in 13% of patients. Malignancy was present in 54% of samples (22% primary lung adenocarcinoma (ADC), 17% squamous carcinoma (SCC), 9% small cell neuroendocrine carcinoma, 2% metastatic malignancy, and 4% other. There was insufficient material for diagnosis in 4% of patients and 5% were of insufficient cellularity for PDL1. Insufficiency rates compare favourably with published data. PDL1 was positive in 63% of adenocarcinomas tested (42% of ADCs underwent immunohistochemistry) and in 75% of SCCs (57% of SCCs underwent immunohistochemistry). One EGFR mutation (L858R) was identified and there were no ALK1 translocations. The incidence of EGFR mutation appears to be half the expected rate in our population. Conclusions EBUS FNAC specimens can be used effectively for diagnosis and staging whilst leaving sufficient cells for ancillary tests that inform subsequent patient management.