Usefulness of diffusion-weighted MR imaging for differentiating between Warthin's tumor and oncocytoma of the parotid gland.

PURPOSE: To assess the efficacy of diffusion-weighted (DW) MR imaging for differentiating between Warthin's tumor and oncocytoma of the parotid gland.

METHODS

Forty-five histopathologically confirmed parotid gland tumors (41 Warthin's tumors and 4 oncocytomas) were examined by MR imaging including DW imaging. 18F-fluorodeoxyglucose PET/CT was also performed in 9 Warthin's tumors and 3 oncocytomas. We retrospectively reviewed the images and compared the MR signal intensities, apparent diffusion coefficients (ADCs), and maximum standardized uptake values (SUVmax) of the solid components between the two pathologies.

RESULTS

The signal intensity ratios (SIRs) on both T2-weighted images (0.92 ± 0.18 vs 0.65 ± 0.13, p < 0.01) and DW images (1.24 ± 0.42 vs 0.43 ± 0.16, p < 0.001) were higher in Warthin's tumors than in oncocytomas. ADCs (0.79 ± 0.11 vs 1.06 ± 0.06 × 10-3 mm2/s, p < 0.001) were lower in Warthin's tumors than in oncocytomas. No significant differences in the SIRs on T1-weighted images (1.09 ± 0.12 vs. 0.99 ± 0.07, p = 0.051) and SUVmax (8.22 ± 3.86 vs. 8.11 ± 1.33, p = 0.864) were found between Warthin's tumor and oncocytoma.

CONCLUSION

DW imaging with ADC measurements is useful for the differentiation of Warthin's tumor from oncocytoma of the parotid gland.