Primary salivary gland tumors from a pathology perspective : Morphomolecular peculiarities and diagnostic and therapeutic challenges

Abstract

Similar to tumors of other organs, salivary gland neoplasms were historically viewed as asingle neoplastic entity and mostly treated as such. Accordingly, only the clinical tumor stage, and not the histological subtype, was considered to be of significant prognostic impact. However, over the years, several distinct sub-entities have been characterized based on morphological features, such as adenoid cystic carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, and salivary duct carcinoma. Most importantly, the nosology of salivary gland carcinomas has undergone adynamic "splitting" on the basis of morphological, immunophenotypic, and molecular characteristics, so that 21independent carcinomas are now listed in the current World Health Organization (WHO) classification. Moreover, it has become evident that splitting of these carcinoma subtypes no longer represents a"pathologist's hobby," but carries significant prognostic and therapeutic relevance for optimized cancer surgery and potentially systemic therapy. The current review summarizes the major features of salivary gland tumors, both benign and malignant, and gives an account of their classification systems and genetic profiles.