Importance of magnetic resonance in the diagnosis of pleomorphic parotid adenoma. Clinical case series.

BACKGROUND Parotid tumours account for approximately 3% of head and neck neoplasms, of which nearly 80% are benign. The most common being the Pleomorphic Adenoma (PA). Our objective was to analyze the morphological characteristics of the PA by Magnetic Resonance (MRI scan) and how it behaves in advanced diffusion (ADC-Apparent Diffusion Coefficient- value) and perfusion sequences. MATERIAL AND METHODS Descriptive and inter-observer study of patients with a suspected PA diagnosis in an MRI scan and subsequent histological confirmation. All studies were carried out with the same MRI. The MRI protocol included enhanced sequences in T1 (T1W), T2 (T2W) diffusion study (DWI) and enhanced sequences in T1 with fat saturation (T1W FS) after injecting the contrast. RESULTS Of 113 patients that underwent magnetic resonance imaging due to a palpable nodule in the parotid region, a radiological diagnosis of parotid gland carcinoma (PGC) was established in 56 patients. Thirteen were excluded due to a prior histopathological diagnosis, 39 of the 43 cases with suspected PA were confirmed (90.67%). They were morphologically well-defined homogeneous tumors, with an average value of high ADC (1.85x10-3mm2/s) and a type A perfusion curve (associated to benignity). The inter-observer concordance was 100%. CONCLUSIONS PAs show typical morphological characteristics in an MRI scan. In case of diagnostic doubt, the diffusion and perfusion sequences help establish a definitive diagnosis.