Concordance of fine needle aspiration cytology and final histology of salivary gland tumours.

Background: Fine needle aspiration cytology (FNAC) is a widely used diagnostic tool to evaluate salivary gland tumours. The Milan system for reporting salivary gland cytopathology allows for standardisation and facilitates cytologicalhistological correlation. However, FNAC findings can still pose a diagnostic challenge. The accuracy of FNAC should be assessed at each centre. The aim of this study was to assess the concordance of FNAC and final histology of salivary gland tumours in three academic hospitals affiliated with the University of Pretoria, South Africa.

Methods: The study was a cross-sectional retrospective analytical study of 214 patients who underwent an operation for salivary gland tumours. All patients with FNAC and histology results between 2007-2017 were included. Patients were recruited from three University of Pretoria, South Africa, affiliated hospitals: Steve Biko Academic, Kalafong Provincial Tertiary and Tembisa Provincial Tertiary Hospital.

Results: Of the 214 patients with salivary gland tumours, the majority were located in the parotid gland (56.1%). Pleomorphic adenoma was the most common tumour (62.6%). The FNAC sensitivity, specificity and diagnostic accuracy (receiver operating characteristic) were 92.7%, 98.1% and 0.95 respectively. The concordance between salivary gland tumour FNAC and final histology was 96.95% with a Cohen's kappa coefficient of 0.91 (p= 0.0001).

Conclusion: There is strong concordance between FNAC and histology of salivary gland tumours. FNAC is an accurate, minimally invasive diagnostic tool with high sensitivity and specificity. It provides the clinician with a reliable preoperative diagnosis determining whether the salivary gland tumour is benign or malignant.