Molecular signature of salivary gland tumors: potential use as diagnostic and prognostic marker

Salivary gland tumors are a highly heterogeneous group of lesions with diverse microscopic appearances and variable clinical behavior. The use of clinical and histological parameters to predict patient prognosis and survival rates has been of limited utility, and the search for new biomarkers that could not only aid in a better understanding of their pathogenesis but also be reliable auxiliaries for prognostic determination and useful diagnostic tools has been performed in the last decades with very exciting results. Hence, gene rearrangements such as CRTC1-MAML2 in mucoepidermoid carcinomas have shown excellent specificity, and more than that, it has been strongly correlated with low-grade tumors and consequently with an increased survival rate and better prognosis of patients affected by neoplasms carrying this translocation. Moreover, MYB-NFIB and EWSR1-ATF1 gene fusions were shown to be specifically found in cases of adenoid cystic carcinomas and hyalinizing clear cell carcinomas, respectively, in the context of salivary gland tumors, becoming reliable diagnostic tools for these entities and potential therapeutic targets for future therapeutic protocols. Finally, the identification of ETV6-NTRK3 in cases previously diagnosed as uncommon acinic cell carcinomas, cystadenocarcinomas, and adenocarcinomas not otherwise specified led to the characterization of a completely new and now widely accepted entity, including, therefore, mammary analogue secretory carcinoma in the list of well-recognized salivary gland carcinomas. Thus, further molecular investigations of salivary gland tumors are warranted, and the recognition of other genetic abnormalities can lead to the acknowledgment of new entities and the acquirement of reliable biomarkers. (AU)