MR imaging of parotid mass lesions: attempts at histopathologic differentiation.

Thirty-four parotid lesions were examined with magnetic resonance imaging. The lesions were studied for a number of factors including size, T1 signal (relative to muscle), T2 signal (relative to CSF), homogeneity, associated adenopathy, associated abnormality of the deep cervical fascia, infiltration of subcutaneous fat, and seventh nerve involvement. Lesions histologically diagnosed as pleomorphic adenoma (benign mixed cell tumor) were predominantly homogeneous as well as smoothly marginated. Those diagnosed as papillary cystadenoma lymphomatosum (Warthin tumor), although equally well marginated, were strikingly heterogeneous, often with areas of hemorrhage. Malignancies and inflammatory masses were both associated with cervical lymphadenopathy; however, inflammatory masses demonstrated fascial thickening of the deep cervical fascia and infiltration of subcutaneous fat ("dirty" fat).