Characteristic bright signal of parotid pleomorphic adenomas on T2-weighted MR images with pathological correlation.

The purpose of this study was to correlate the MR features and histological findings of pleomorphic adenomas, which are the most common tumour of the parotid gland, and to distinguish them from other types of tumour in the parotid gland. The materials studied consisted of 20 pleomorphic adenomas, including 12 untreated and eight recurrent cases, 17 other benign parotid tumours, and 12 malignant tumours. T1- and T2-weighted images and Gd-DTPA enhanced T1-weighted images were obtained. Characteristic bright signals with a higher intensity than that of CSF were seen in all of the pleomorphic adenomas on T2-weighted images, and were found to represent myxoid areas histologically. Although the cystic spaces in some benign tumours produced bright signals, these areas were distinguished from myxoid areas due to nonenhancement with Gd-DTPA. No bright signals were seen in the malignant tumours. In conclusion, bright signals on T2-weighted images represent myxoid tissue and are useful findings for diagnosing pleomorphic adenomas.