The Efficacy of Touch Smear Cytology in the Diagnosis of Salivary Gland Cancers

Purpose: Methods for cytologic diagnosis, such as fine-needle aspiration (FNA) and touch smear (TS) cytology, have been frequently used for malignant tumor screening; however, false-negative cases often result in misdiagnosis. The purpose of this study was to investigate the causes of false-negative cases and methods to decrease the false-negative rate in salivary gland tumor TS cytology.

Materials and methods: In this cross-sectional study, the authors examined pathologically confirmed salivary gland tumors in 127 cases in which FNA and TS cytology were performed before the operation or open biopsy at Numazu City Hospital (Numazu, Japan) from 2002 to 2016. The authors evaluated the false-negative rates of TS and FNA cytology separately and when used in combination and other variables, such as age, gender, sensitivity, accuracy, specificity, and overall pathologic diagnosis by resection.

Results: The overall false-negative rate of postoperative pathologic diagnosis was lower when TS and FNA were combined (1 of 127 cases; 0.8%) compared with FNA cytology alone (10 of 127 cases; 7.9%; P = .034). Suggested causes of a false-negative FNA (or TS) result include cytologic difficulties present in certain malignancies, such as mucoepidermoid carcinoma, adenoid cystic carcinoma, and others.

Conclusion: False-negative cases were decreased when a combination of preoperative FNA and intraoperative TS cytology was performed. TS cytology appears to be a useful method to avoid misdiagnosis in salivary gland diseases.