Abstract: Background and purpose: Basal cell adenoma (BCA) of the parotid gland has low incidence and high misdiagnosis rate in clinical practice. So far, the report on the MRI manifestation of BCA is rare. Our study combined dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) with diffusion weighed imaging (DWI) to investigate the MRI features of BCA of the parotid gland and its correlation with pathologic features. Methods: We retrospectively analyzed the correlation of MRI findings and pathology in 26 patients with histopathologically proven BCA of the parotid gland. The clinical presentation, pathologic features and localization, size, number, shape, signal, enhancement pattern of tumor were analyzed. Results: In this study, 18 patients (69.2%) were female and 8 patients (30.8%) were male. The median age was 51 (range 32-72) years. Twenty-five patients (96.2%) had single lesion and only one patient (3.8%) had two. The average size of the 27 lesions was 22 (range 11-36) mm. Thirteen lesions were located in superficial lobe, 5 in deep lobe and 9 across both lobes. All the 27 lesions had clear margin without lobular appearance and 25 lesions had complete or incomplete hypo-intensity rim in T2WI. Compared with neck muscle, all 27 lesions showed iso- or hyper-intense in T1WI and hyper-intense in T2WI. Twenty-one lesions (77.8%) had cystic change with varying size. The signal intensities of solid part of lesions were homogeneous in 21 lesions, heterogeneous in 6. Twenty-one lesions (77.8%) showed persistent enhancement and 6 (22.2%) had outflow enhancement. DWI was performed in 9 patients (10 lesions), the mean ADC value was (1.22±0.20)×10^-3 mm²/s. Under microscope, it consisted of a monomorphic population of basaloid epithelial cells, organized with prominent basal cell layer and distinct basement membrane-like material, lacking the myxochondroid stromal component. Conclusion: BCA of the parotid gland has certain clinical and MRI features. Analysis of the correlation between the MRI findings and the pathologic features may be helpful in making qualitative and differential diagnosis of BCA.

Key words: Parotid gland, Basal cell adenoma, Magnetic resonance imaging, Pathology