1996 Volume 89 Issue 4 Pages 479-484
We surveyed MRI (magnetic resonance images) of 105 parotid tumors including 51 Pleomorphic adenomas and assessed the usefulness of MR findings in differentiating pleomorphic adenomas from other benign tumors and malignant tumors.
It was reported that pleomorphic adenomas show a low signal intensity on T1-weighted images, a high signal intensity on T2-weighted images, and well-defined margins with an inhomogeneous internal structure on MRI. In our results, low signal intensity on T1-weighted images, well-defined margins, and an inhomogeneous internal structure were essential findings for the diagnosis of pleomorphic adenomas in MRI. However, these features were often shown in other benign and malignant tumors. High signal intensity on T2-weighted images was an essential finding for diagnosis of pleomorphic adenomas and showed relatively high specificity to pleomorphic adenoma when compared with other parotid tumors.
Although rim formation around the tumor and lobulated contour as MR features of pleomorphic adenomas were not observed frequently on MRI of pleomorphic adenomas, these did show a high specificity for those tumors, indicating that these features are useful for differential diagnosis of pleomorphic adenomas from other benign and malignant tumors.
Histopathological study indicated that rim formation around the tumor and lobulated contour observed in MRI corresponded to capsule formation and lobulated growth of pleomorphic adenomas, respectively.
