Quantitative diffusion-weighted magnetic resonance imaging in the evaluation of parotid gland masses: a study with histopathological correlation.

We evaluated the quantitative diffusion-weighted magnetic resonance imaging (DW-MRI) for parotid masses. Seventy-five patients with 81 focal parotid masses were included. Following DW-MRI, 73 masses underwent surgical biopsy/resection, 6 underwent ultrasonography-guided fine-needle aspiration, and 2 underwent both procedures. The mean apparent diffusion coefficient (ADC) of benign tumors (n=49, 1.72×10(-3) mm(2)/s) was higher than that of malignant tumors (n=32, 1.05×10(-3) mm(2)/s) (P<.001). ADC was 2.15×10(-3) mm(2)/s for pleomorphic adenomas, which was higher than that for other tumors (P<.001 for all). ADC cutoff was 1.315 for distinguishing between pleomorphic adenomas and others including malignant tumors. Therefore, DW-MRI may be useful for distinguishing between pleomorphic adenomas and other parotid masses.