MRI diagnostics of pleomorphic adenomas of salivary glands. New extended evaluation criteria

Abstract

Summary. MRI is one of the important methods of the salivary gland tumor (pleomorphic adenomas) diagnostics at presurgical stage. It allows for determination of not only the localization of the tumor and its structural peculiarities, but also the topography of the surrounding tissues, determination of the possible changes in the surrounding tissues. The application of MRI in salivary glands PA diagnostics will enable the extension of its evaluation criteria and will determine its peculiarities.

The aim of the study – to determinate of new extended diagnostic criteria of pleomorphic adenomas of the salivary glands by virtue of MRI diagnostics.

Materials and Methods. The material of the study included 30 patients with major salivary glands tumor (pleomorphic adenomas), who has undergone treatment at the Department of Maxillofacial Surgery No. 2 of Kyiv City Clinical Hospital No.12 for the period from 2018 to 2020. All patients underwent general clinical assessment. The removed material was subject to histopathological examination. The magnetic resonance imaging was conducted by means of Toshiba Vantage Titan 1.5T MRI scanner.

Results and Discussion. The conducted MRI of the patients with the salivary gland pleomorphic adenomas showed that in all patients the tumor was represented by one nodule, with tuberous surface and deformed capsule in 20 (60 %) cases, heterogeneity of the capsule – 0.68±0.24 mm, and the largest size of the tumor in vertical view – 25.32±11.11 mm, mean ratio of the tumor volume to gland volume – 0.24±0.27 (23 %), local dilation of the gland ducts near the tumor in 15 (50 %) patients, homogeneity of non-capsular tumor – 183.7±85.47, mean optical density on Т2 TSE ВІ – 1428.8±881.69, apparent diffusion coefficient (x10-3 mm2/s) – 1.88±0.41, distance from the tumor surface to the skin – 5.061±2.34 mm.

Conclusions. The conducted MRI examinations enabled for determination of 5 groups of parameters which are required to be used for the description of the salivary glands PA (general tumor parameters, quantitative parameters of the tumor density; tumor capsule characteristics; size of the gland, tumor and their localization; presence of the inflammatory changes in the surrounding tissues of the tumor). The analysis of the statistical confidence between the groups of MRI parameters revealed the peculiarities depending on tumor localization – in parotid or submandibular glands – and presence of the inflammatory changes and condition of tumor capsule. The parotid gland PA were characterized by the lesser thickness of the tumor capsule and the greater vertical size of the gland as compared to submandibular gland PA, which was more homogeneous, non-capsular. The marked sign of the tumor capsule heterogeneity (difference of more than 0.5 mm) was observed in the majority of the patients with the local dilation of the ducts.