Endobronchial ultrasound‐guided fine‐needle aspiration cytology of bronchial low‐grade mucoepidermoid carcinoma: Rapid on‐site evaluation of cytopathologic findings

Abstract

Bronchial mucoepidermoid carcinoma (MEC) is rare, comprising about 0.2% of primary lung tumors. Endobronchial ultrasound (EBUS) guided fine-needle aspiration (FNA) cytology is an integral tool in the diagnosis and staging of malignant lung tumors. Rapid on-site evaluation (ROSE) has been proven useful as a guide for assessing the adequacy and accuracy of the FNA samples. Therefore, comprehensive knowledge of diagnostic cytomorphologic findings of MEC is critical for ROSE. We reported a 46-year-old woman with 6 weeks of cough productive of yellow sputum that did not improve on antibiotics. A chest CT demonstrated a well-circumscribed nodule in the right lower lobe bronchus that extended into the lung parenchyma. EBUS-guided FNA was performed to obtain diagnostic materials. The ROSE of cytology specimen revealed numerous tight clusters of cells with well-defined, but scant cytoplasm. These cells were relatively small and bland with high N/C ratio, resembling benign ductal cells. Neither cilia nor intranuclear inclusions were noted. Focal extracellular metachromatic mucinous materials were also noted. A preliminary diagnosis of "low-grade epithelial neoplasm, favor low grade MEC" was rendered. The definitive diagnosis was confirmed by both cytology and core biopsy. EBUS-guided FNA cytology can be a reliable method for the diagnosis of bronchial low grade MEC. The cyto-morphology of ROSE can indicate the diagnosis of low grade MEC and direct the appropriate follow-up triage of the specimen.