Reduced percentage of inconclusive reports and need for repeated fine needle aspirations in ultrasound versus free-hand parotid cytology

Abstract

Abstract Background Fine needle aspiration cytology has been established as a minimally invasive, non-tumour seeding investigation of choice in the initial diagnostic pathway of parotid lesions. The purpose of this study was to compare the accuracy of fine needle aspiration cytology performed with and without ultrasound to determine whether one method should be preferred to the other. A retrospective review of all patients undergoing fine needle aspiration cytology with and without ultrasound for parotid masses in a large district general hospital between 2012 and 2016 was performed. Specificity, sensitivity, accuracy, positive and negative predictive value, percentage of inconclusive fine needle aspiration cytology and percentage of second fine needle aspiration cytology were determined for each group. Results A total of 397 fine needle aspiration cytology results were available for analysis. The numbers performed with ultrasound guidance and free-hand were roughly equal (208 (52.3%) versus 189 (47.7%)). The number of inconclusive fine needle aspiration cytology reports was significantly higher in the free-hand group (65/189 (34.4%)) than the ultrasound group (25/208 (12%)) (p < 0.0001). A significantly higher number of repeated fine needle aspiration cytology were undertaken in the free-hand group vs ultrasound group (43 vs 15, p < 0.0001); overall 7.2% of ultrasound-guided fine needle aspiration cytology required a second fine needle aspiration cytology, compared to 22.8% in the free-hand group. The sensitivity, specificity, positive and negative predictive values were all higher in the ultrasound group versus the free-hand group. Conclusions Ultrasound-guided fine needle aspiration cytology is superior to free-hand fine needle aspiration cytology in the investigation of parotid tumours. There is a significant benefit in reducing the number of inconclusive results and repeat fine needle aspiration cytology, and a potential benefit in improving the sensitivity and positive predictive value, when immediate cytology assessment of the sample quality is not performed.