Pleomorphic adenoma of salivary glands: common and uncommon CT and MR imaging features.

Pleomorphic adenoma (PA) is the most common salivary gland tumor and is characterized by cytomorphological and architectural diversity. On CT and MR images, PAs are shown as well-defined lesions occasionally accompanied by characteristic lobulated contours. On T2-weighted images, typical PAs show marked hyperintensity, which reflects the abundant myxochondroid stroma, with a hypointense rim indicating the fibrous capsule. However, intratumoral signal intensity varies according to the cellular density, proportion of epithelial and stromal components, and type of stromal components. In addition, a variety of secondary histological changes, including fibrosis, lipometaplasia, ossification, cystic degeneration, and infarction, occur rarely in PAs; therefore, they are associated with difficulty in differential diagnosis from other salivary gland tumors. This review article describes the common and uncommon CT and MR imaging features of PA of the salivary glands.