Parotid gland tumors: Comparison of conventional and diffusion-weighted MR imaging findings with histopathological

Abstract

The aim of this study was to determine the relationship between histopathological results and conventional magnetic resonance imaging (MRI), diffusion-weighted imaging findings of parotid gland tumors and the possible contribution of apparent diffusion coefficient (ADC) to diagnosis. Material and Methods: Sixty patients with parotid masses diagnosed using histopathology and/or cytology were enrolled in this retrospective study. All patients were evaluated using a 1.5 Tesla MRI. Demographic features, conventional MRI findings, and ADC values (mean, minimum, maximum, and relative) were recorded. MRI findings and ADC values were compared between benign-malignant groups and pleomorphic adenoma versus Warthin's tumor groups. Results: Sixty tumors (48 benign, 12 malignant) were evaluated in a total of 60 patients (39 males, 21 females). The mean age was 59 (±14, 18-86) years; the mean lesion size was 26 (±10, 11-61) mm. On the texture of conventional MRI, T2 dominantly hyperintense/with hypointensity signal was seen in 87% of pleomorphic adenomas and T2 dominantly hypointense/with hyperintesity signal was encountered in 64% of all Warthin's tumors. Seven (28%) Warthin's tumors were misdiagnosed as pleomorphic adenomas and two others (8%) as malignant tumors. Commonly used mean ADC value was 1.6±0.6×10−3 mm2/s for benign tumors, 0.8±0.3×10-3 mm2/s for malign tumors, 1 (0.9-1.8)×10-3 mm2/s for Warthin's tumors, and 1.9±0.3×10-3 mm2/s for pleomorphic adenomas. There was a statistically significant difference in ADC values between benign-malignant tumors and pleomorphic adenomas-Warthin's tumors. Conclusion: Warthin's tumor may occasionally be misdiagnosed as pleomorphic adenoma and malignant tumor because of variable morphologic features. In addition to benign-malignant differentiation, the added ADC measurement may also be useful for differentiating Warthin's tumors from pleomorphic adenomas.