Classification of head and neck tumors has evolved in recent decades including a widespread application of molecular testing in tumors of the salivary glands, sinonasal tract, oropharynx, nasopharynx, and soft tissue. Availability of new molecular techniques allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, the expanding spectrum of immunohistochemical markers facilitates a rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined classifications, while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review highlights some principal molecular alterations in head and neck neoplasms presently available to assist pathologists in the practice of diagnosis, prognostication and prediction of response to treatment.

• Keywords
• Head and neck, Molecular diagnostics, Next-generation sequencing, Salivary gland, Sinonasal tumor, Soft tissue,
• MeSH
• Immunohistochemistry MeSH
• Humans MeSH
• Pathology, Molecular * MeSH
• Head and Neck Neoplasms * diagnosis   genetics   MeSH
• Pathologists MeSH
• Salivary Glands MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

Diagnosis of salivary gland neoplasms is often challenging due to their high morphological diversity and overlaps. Several recurrent molecular alterations have been described recently, which can serve as powerful diagnostic tools and potential therapeutic targets (e.g. NTRK or RET fusions). However, current sequential molecular testing can be expensive and time consuming. In order to facilitate the diagnosis of salivary gland neoplasms, we designed an all-in-one RNA-based next generation sequencing panel suitable for the detection of mutations, fusions and gene expression levels (including NR4A3) of 27 genes involved in salivary gland neoplasms. Here we present the validation of the "SalvGlandDx" panel on FFPE histological specimen including fine needle aspiration (FNA) cell block material, against the standard methods currently used at our institution. In a second part we describe selected unique cases in which the SalvGlandDx panel allowed proper diagnosis and new insights into special molecular characteristics of selected salivary gland tumors. We characterize a unique salivary gland adenocarcinoma harboring a ZCCHC7-NTRK2 fusion, a highly uncommon spindle cell and pseudoangiomatoid adenoid-cystic carcinoma with MYBL1-NFIB fusion, and a purely oncocytic mucoepidermoid carcinoma, whereas diagnosis could be made by detection of a CRTC3-MAML2 rearrangement on the cell block specimen of the FNA. Further, a rare case of a SS18-ZBTB7A rearranged low-grade adenocarcinoma previously described as potential spectrum of microsecretory adenocarcinoma, is reported. In addition, features of six cases within the spectrum of polymorphous adenocarcinoma / cribriform adenocarcinoma of salivary gland including PRKD1 p.E710D mutations and novel fusions involving PRKAR2A-PRKD1, SNX9-PRKD1 and ATL2-PRKD3, are described.

• Keywords
• Biopsy, Comprehensive, FNA, Molecular, Salivary gland neoplasm, Testing,
• MeSH
• Biopsy MeSH
• Oncogene Proteins, Fusion genetics   metabolism   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Immunohistochemistry methods   MeSH
• Humans MeSH
• Mutation MeSH
• Biomarkers, Tumor * MeSH
• Cell Line, Tumor MeSH
• Salivary Gland Neoplasms diagnosis   drug therapy   genetics   MeSH
• Neoplasm Staging MeSH
• Gene Expression Profiling * methods   MeSH
• Neoplasm Grading MeSH
• High-Throughput Nucleotide Sequencing * methods   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Oncogene Proteins, Fusion MeSH
• Biomarkers, Tumor * MeSH