Inter- and Intratumoral Variability in Magnetic Resonance Imaging of Pleomorphic Adenoma: An Attempt to Interpret the Variable Magnetic Resonance Findings

Objectives: The purpose of our study was to describe the various magnetic resonance (MR) findings of pleomorphic adenoma and to interpret these findings. Methods: MR studies of 33 pleomorphic adenomas and 13 malignant tumors in the major salivary glands were reviewed. Results: High signal intensity on short-inversion-time inversion recovery (STIR) and T2-weighted (T2W) images, progressive enhancement on dynamic MR images, and high apparent diffusion coefficient (ADC) values on diffusion-weighted (DW) images reflected myxoid-dominant components in pleomorphic adenomas. Hypercellularity with less-myxoid stroma showed reduced signal intensity on STIR and T2W images and also reduced ADC values on DW images, and the peak of time versus signal intensity curves (TICs) was reached earlier on dynamic MR images. Conclusions: The MR images of hypercellularity components in pleomorphic adenoma overlap with those of malignant parotid tumors. Detecting myxoid components by STIR, T2W, DW, and dynamic MR images is useful for predicting whether salivary gland tumors are pleomorphic adenoma or not.