Conventional and Diffusion-Weighted MR Imaging Findings of Parotid Gland Tumors.

Objective: To investigate diffusion-weighted magnetic resonance imaging (MRI) findings of parotid gland lesions in addition to conventional MRI findings and demographic data.

Methods: A retrospective evaluation was made of the demographic data, histopathologic data, preoperative conventional and diffusion-weighted MRI of 74 patients who underwent parotidectomy. The patients were categorized according to the histopathology (pleomorphic adenoma [PA], Warthin's Tumor [WT] and malignant Tumor [MT]).

Results: Histologically, 30 patients had PA, 27 patients had WT, and the remaining 17 patients had MT. The mean age of the PA, WT and MT groups were 44±21 (20-72), 55±10 (41-71) and 62±20 (21-76) years, respectively. The WT (81%) and MT (70%) groups were male dominant, while the PA group showed female dominance (55%). The PA group showed statistically significant difference in terms of age (p<0.05) and gender (p=0.009) compared to the other two groups. The median apparent diffusion coefficient (ADC) values for the PA, WT and MT groups were 1.99±0.94 (1.10-2.41) × 10-3 mm2/s, 0.92±0.35 (0.21-1.79) × 10-3 mm2/s and 1.20±0.34 (0.78-1.47) × 10-3 mm2/s, respectively. PA was differentiated from the other two groups (p=0.001). The sensitivity and specificity for distinguishing PAs from WT was 97% and 85%, respectively, when the ADC cutoff value was 1.25; and for distinguishing PAs from MT was 77% and 83%, respectively, when the ADC cutoff value was 1.35.

Conclusion: ADC measurements are useful for the differentiation of PA from both WT and MT; and can be used as a complementary tool to predict the histopathology in the preoperative planning of parotid tumors.