Introduction: Cytology is commonly used to diagnose non-small cell lung cancer (NSCLC) but is an inaccurate means of diagnosis of bronchioloalveolar carcinoma (BAC). The aims of this study were to calculate the sensitivity and specificity of cytologic diagnosis of BAC and to estimate the misclassification of BAC as other subtypes of NSCLC.
Methods: Preoperative fine-needle aspiration cytology diagnoses were compared to histology diagnoses in 222 patients, including 51 patients with pure or mixed BAC, who underwent lung resection for NSCLC at our institution since 1999.
Results: The sensitivity and specificity of a cytologic diagnosis of BAC were 12% and 99%, respectively. Based on cytologic diagnosis, 63% of BAC was misclassified as adenocarcinoma, and 18% was misclassified as undifferentiated NSCLC. In this cohort, 35% of adenocarcinomas and 12% of undifferentiated NSCLC diagnosed by cytology had BAC histology.
Conclusions: Diagnosis of NSCLC by cytology alone results in significant misclassification of BAC, most commonly as adenocarcinoma or undifferentiated NSCLC. Because patients with BAC respond differently to certain treatments such as endothelial growth factor receptor inhibitors and surgical resection of multifocal lung cancer, misclassification of BAC may have important therapeutic implications.