Clinical decision-making and risk of malignancy when parotid gland fine needle aspiration cytology indicates a non-neoplastic or non-diagnostic finding.

Introduction: Non-neoplastic and non-diagnostic cytological findings present a diagnostic and therapeutic challenge in Head and Neck oncology. Both groups still harbor a risk of malignancy (ROM). Of note, ROM values have been counted from surgically confirmed lesions only. The purpose of this study was to evaluate the clinical course of patients with non-neoplastic or non-diagnostic fine needle aspiration cytology (FNAC) findings from a parotid gland lesion.

Methods: This retrospective cohort study comprises all 184 consecutive patients who visited the Department of Otorhinolaryngology - Head and Neck Surgery, Helsinki University Hospital (HUS, Helsinki, Finland) and whose first parotid gland FNAC result during 2016-2018 was non-neoplastic or non-diagnostic. The cytology reports were obtained from the HUS Pathological Archives (Q-Pati). Demographics, physical examination findings, and cytopathological and treatment data were reviewed. Two patient groups were formed according to their clinical management: those who had surgery and those who were only followed up. If the parotid gland was operated on, FNAC was compared with histology. If the patient was followed up without surgical treatment, the follow-up data included a review of the patient records supplemented with a questionnaire.

Results: Altogether, there were 186 parotid lesions. Seventy-six (40.9%) tumors in 75 patients were operated on, and 110 (59.1%) were only followed up. Of all parotid gland lesions, 12 (6.5%) turned out to be malignant, and all of them were in the surgically treated group. When only followed up clinically, with repeated needle sampling or imaging during the minimum four-year follow-up period, none of the other lesions turned out to be malignant.

Conclusion: The risk of malignancy for non-diagnostic and non-neoplastic FNAC samples is lower when all FNAC samples, including also those from non-surgically treated patients, are included in comparison with the series that includes only surgically treated patients with histopathological confirmation. Our results suggest that this patient group can be followed up conservatively in the absence of abnormal symptoms or radiological findings.