An integrated approach to the morphological diagnosis of different types of pleomorphic adenomas of the salivary gland: long-term research results

Abstract

Introduction. Morphological research methods play an important role in the diagnosis of pleomorphic adenoma in the preoperative and postoperative periods. Pleomorphic adenoma is histologically extremely heterogenous and has a complex structure, which sometimes causes certain difficulties and misdiagnosis for pathologists in the morphological diagnosis of this tumor and its histological variant determination. Pathologists emphasize that pleomorphic adenoma may be confused with myoepithelioma, adenoid cystic carcinoma, mucoepidermoid carcinoma, basal cell adenoma because of its varied histopathological presentation. The results of our own long-term research allow us to identify certain morphological features of various pleomorphic adenomas and, on their basis, to formulate an integrated approach to the morphological diagnosis of these tumor variants. The aim is to describe an integrated approach to the morphological diagnosis of different types of pleomorphic adenomas of the salivary gland. Materials and methods. Surgical and biopsy material from 30 patients with pleomorphic adenomas of epithelial, mixed and mesenchymal variants was studied using histological, immunohistochemical, genetic, morphometric and statistical methods. Results. The results of research allowed us to identify methods for determination the pleomorphic adenomas types. The first method requires an immunohistochemical reaction with a monoclonal antibody to human papillomavirus type 16, followed by counting the percentage of positively stained cells in the tumor. Thus, the mesenchymal variant of the tumor is diagnosed when the percentage of positively stained cells is < 40%. In the mixed variant, this indicator is ≥ 40%, but ≤ 70%, and in epithelial variant – > 70%. The second method was based on the multivariate discriminant analysis. Three formulae were derived to determine the tumor types (Fmesenchymal = - 41.03 + 4.96Х1 + 1.11Х2, Fepithelial = - 22.27 + 3.46Х1 + 0.85Х2, Fmixed = - 122.25 + 5.63Х1 + 3.2Х2, here Х1 - number of vessels, Х2 – specific volume of parenchyma). Conclusions. The authors identified several methods for determining the histological variants of pleomorphic adenomas. These methods will improve the morphological diagnosis of pleomorphic adenomas variants in the preoperative and postoperative periods.