[Conventional and functional MRI features of parotid Warthin tumor: correlation with clinicopathological findings]

Objective: To assess the conventional and functional MRI features of parotid Warthin tumor (adenolymphoma) and to investigate the correlation between MRI and clinicopathological features which can provide evidence for clinical diagnosis and treatment. Methods: Sixty-seven patients with parotid Warthin tumor who were treated in the Department of Stomatology, The Fifth Clinical Medical College of Yangzhou University, Changshu No. 2 People's Hospital from June 2008 to April 2017 were included in this study. The retrospective study evaluated preoperative conventional and functional MRI features and clinicopathological findings of this group of patients. Among 67 patients (65 males, 2 females) with 92 lesions, there were 16 patients with multiple lesions and others with single lesion. Their age was (62.1±8.8) years, ranging from 42 to 84 years. According to pathological features, parotid Warthin tumor were classified into two types. Type Ⅰ was predominantly solid component which included completely solid or solid tumor with some cystic components. Type Ⅱ was predominantly cystic component which was characterized by big cyst with some solid components, and could be divided into capsule-like and scum-like cystic type, based on whether its interface of solid and cystic component was clear or not. On contrast-enhanced MRI, according to whether the lesion showed enhancement or not, solid or cystic component was defined. Results: Seventy-two lesions were located in the lower pole of the parotid gland, of which sixty-eight lesions were located in posterior inferior quadrant. In addition, sixteen lesions were located in the upper pole and four lesions in the middle. Because MRI features were consistent with pathological findings, parotid Warthin tumor were classified into solid (73) and cystic types (19). On T2WI, solid components showed isointense (92), whereas on T1WI cystic components demonstrated hyperintense (90). On contrast enhanced T1WI, solid types showed marginal vasculature sign (73), mild (69) or moderate (4) enhancement, whereas its cystic component showed no enhancement. On contrast enhanced T1WI, cystic types showed ring-like enhancement of cycle-wall and intra-cystic septal linear enhancement, whereas its solid components demonstrated mild enhancement (19). On diffusion weighted imaging, these masses demonstrated hyperintensity and lower apparent diffusion coefficient value indicating restricted diffusion (59/59). On dynamic contrast-enhanced-MRI, the masses showed "wash-out" pattern (28/29) or plateau pattern (1/29). Conclusions: Parotid Warthin tumor mainly occur in the posterior inferior quadrant of parotid gland and mostly in mid-aged or elder men. It has certain characteristics on conventional and function MRI. There is correlation between MRI and clinicopathological findings and it is useful for accurate diagnosis and treatment to understand these features.