Patient and tumor characteristics predictive of primary parotid gland malignancy: A 20-year experience at the University of Wisconsin.

PURPOSE: To identify patient and tumor characteristics predictive of primary parotid malignancy. MATERIALS AND METHODS: Records were reviewed for patients who underwent parotidectomy at the University of Wisconsin from 1994 to 2013. Patients with primary parotid neoplasms were separated into benign or malignant subgroups. A multivariate logistic regression model was employed to compare categorical (gender, lesion side, nature of presentation, recurrence) and numerical variables (age, tumor size) between the benign and malignant groups. Mean BMI was compared between the groups by univariate analysis. RESULTS: 771 patients underwent parotidectomy from 1994 to 2013, and 474 had a primary parotid neoplasm. No relationship existed between malignancy and gender (p=0.610), lesion side (p=0.110), or BMI (p=0.196). Mean age (p=0.015) and tumor size (p=0.011) were significantly different between the benign and malignant groups. Patient presentation was classified into three categories: symptomatic (n=109), palpable and asymptomatic (n=303), and incidentally noted on imaging (n=57). From all patients with symptomatic, asymptomatic or incidentally noted masses, 41.3%, 10.6% and 5.3%, respectively, were diagnosed with malignant disease. There was a significant relationship between the patient's initial presentation and malignancy (p<0.001), and patients with facial nerve dysfunction or skin involvement had the greatest likelihood of malignancy. Finally, there was a significant association between malignancy and recurrence (p=0.001). CONCLUSIONS: In this study, age, tumor size, and nature of presentation were all associated with primary parotid malignancy. Understanding the impact of these features on the probability of malignancy is valuable in decision making and counseling of patients presenting with a newly diagnosed parotid neoplasm.