Don't stop the champions of research now: a brief history of head and neck pathology developments

Outcome-oriented clinicopathological reappraisal of sinonasal adenoid cystic carcinoma with broad morphological spectrum and high MYB::NFIB prevalence

Adenoid cystic carcinoma (AdCC) is a salivary gland neoplasm that infrequently appears in the sinonasal region. The aim of this study was to evaluate the outcome and clinicopathological parameters of sinonasal AdCC. A retrospective analysis was conducted on all cases of AdCC affecting the nasal cavity or paranasal sinuses between 2000 and 2018 at the University Hospital Zurich. Tumor material was examined for morphological features and analyzed for molecular alterations. A total of 14 patients were included. Mean age at presentation was 57.7 years. Sequencing revealed MYB::NFIB gene fusion in 11/12 analyzable cases. Poor prognostic factors were solid variant (p < 0.001), histopathological high-grade transformation (p < 0.001), and tumor involvement of the sphenoid sinus (p = 0.02). The median recurrence-free survival (RFS) and OS were 5.2 years and 11.3 years. The RFS rates at 1-, 5-, and 10-year were 100%, 53.8%, and 23.1%. The OS rates at 1-, 5-, and 10- years were 100%, 91.7%, and 62.9%, respectively. In Conclusion, the solid variant (solid portion > 30%), high-grade transformation, and sphenoid sinus involvement are negative prognostic factors for sinonasal AdCC. A high prevalence of MYB::NFIB gene fusion may help to correctly classify diagnostically challenging (e.g. metatypical) cases.

Genetic Rearrangements in Different Salivary Gland Tumors: A Systematic Review

Salivary gland tumors (SGT) encompass a wide range of neoplasms, each with its own unique histological type and clinical presentation. This review hones in on prevalent subtypes of SGTs, including adenoid cystic carcinoma (ACC), salivary duct carcinoma (SDC), and polymorphous adenocarcinoma (PAC). The articles, identified through specific keywords, were meticulously screened in databases like PubMed, Scopus, Google Scholar, and Web of Science from 2018 to 2023. Eight articles delved into genetic modifications among the selected SGT types. A fusion protein known as MYB-NF1B is typically associated with ACC, promoting cell proliferation while inhibiting apoptosis. The presence of MYB modifications in ACCs is a beacon of hope, as it is linked to a more favorable prognosis. In contrast, SDCs often exhibit HER2 expression. The invasive nature of SGTs contributes to their resistance to treatment. In the case of PAC, the role of PRKD1 is particularly noteworthy. PRKD1, integrated with other genes from the PRKD1/2/3 cluster, helps to differentiate PAC from other diseases. Furthermore, the genetic profiles of KTN1-PRKD1) and PPP2R2A:PRKD1 are distinct. The significant genetic variability among SGTs necessitates meticulous examination. This field is in a constant state of evolution, with new discoveries reshaping our understanding. Genetics is a key player in deciphering SGTs and tailoring treatments. This complex neoplasm demands ongoing research to uncover all genetic influences, thereby enhancing diagnostic methodologies, therapeutic strategies, and patient outcomes.

[New information about tumours of the salivary glands : WHO classification 2022]

The WHO 2022 classification of head and neck tumours contains another slight increase in the number of listed benign and malignant tumour entities of the salivary glands. This includes conceptual changes and alterations in the terminology of some entities. While some new features are regarded as preliminary or provisional, others are strongly disputed (for example the terminology of intraductal carcinoma). The impact of molecular findings, mainly recurrent gene fusions, continues to increase rapidly and some have been included in the definition of certain tumour entities. The significance of molecular findings is, however, still largely restricted to diagnostic aspects. Newly included entities include microsecretory carcinoma (defined by an SS18::MEF2C fusion), sclerosing microcystic adenocarcinoma (similar to skin adnexal tumours of the same name) and mucinous adenocarcinoma (characterized by AKT1 mutations with heterogeneous morphology).

Development of head and neck pathology in Europe

This review gives a brief history of the development of head and neck pathology in Europe from a humble beginning in the 1930s to the explosive activities the last 15 years. During the decades before the introduction of immunohistochemistry in the 1980s, head and neck pathology grew as a subspeciality in many European countries. In the late 1940s, the Institute of Laryngology and Otology with its own pathology laboratory was founded in London, and in 1964 the World Health Organization (WHO) International Reference Centre for the Histological Classification of Salivary Tumours was established at the Bland-Sutton Institute of Pathology, also in London. International collaboration, and very much so in Europe, led to the publication of the first WHO Classification of Salivary Gland Tumours in 1972. In the 1960s, a salivary gland register was organised in Hamburg and in Cologne the microlaryngoscopy was invented enabling microscopic endoscopic examination and rather shortly afterwards a carbon dioxide laser attached to the microscope became established and laryngeal lesions could be treated by laser vaporisation. During the last three decades, the use of immunohistochemistry supplemented with cytogenetic and refined molecular techniques has greatly facilitated the pathological diagnostics of head and neck lesions and has had a huge impact on research. Collaboration between different European centres has drastically increased partly due to establishment of scientific societies such as the Head and Neck Working Group (HNWG) within the European Society of Pathology and the International Head and Neck Scientific Group (IHNSG). A very large number of European pathologists have contributed to the 2nd, 3rd and 4th WHO books, and are involved in the upcoming 5th edition. Accredited educational meetings and courses are nowadays regularly arranged in Europe. Numerous textbooks on head and neck pathology have been written and edited by European pathologists. The increased collaboration has created larger series of tumours for research and new entities, mainly defined by their genetic abnormalities, are continuously emerging from Europe, particularly regarding salivary gland neoplasms and "undifferentiated" sinonasal tumours. These findings have led to a better and more precise classification and open the possibilities for new treatment strategies.

An Overview on the Histogenesis and Morphogenesis of Salivary Gland Neoplasms and Evolving Diagnostic Approaches

Simple Summary

Diagnosing salivary gland neoplasms (SGN) remain a challenge, given their underlying biological nature and overlapping features. Evolving techniques in molecular pathology have uncovered genetic mutations resulting in these tumors. This review delves into the molecular etiopatho-genesis of SGN, highlighting advanced diagnostic protocols that may facilitate the identification and therapy of a variety of SGN.

Abstract

Salivary gland neoplasms (SGN) remain a diagnostic dilemma due to their heterogenic complex behavior. Their diverse histomorphological appearance is attributed to the underlying cellular mechanisms and differentiation into various histopathological subtypes with overlapping fea-tures. Diagnostic tools such as fine needle aspiration biopsy, computerized tomography, magnetic resonance imaging, and positron emission tomography help evaluate the structure and assess the staging of SGN. Advances in molecular pathology have uncovered genetic patterns and oncogenes by immunohistochemistry, fluorescent in situ hybridization, and next–generation sequencing, that may potentially contribute to innovating diagnostic approaches in identifying various SGN. Surgical resection is the principal treatment for most SGN. Other modalities such as radiotherapy, chemotherapy, targeted therapy (agents like tyrosine kinase inhibitors, monoclonal antibodies, and proteasome inhibitors), and potential hormone therapy may be applied, depending on the clinical behaviors, histopathologic grading, tumor stage and location, and the extent of tissue invasion. This review delves into the molecular pathways of salivary gland tumorigenesis, highlighting recent diagnostic protocols that may facilitate the identification and management of SGN.

Why is the histomorphological diagnosis of tumours of minor salivary glands much more difficult?

AIMS

There is a widespread perception among clinicians and pathologists that the histomorphological assessment of minor salivary gland (MinSG) tumours is more difficult and hampered by more misdiagnoses than that of major salivary gland tumours. This is based on a vague, subjective clinical impression, lacking scientific proof. The aim of the present study was to identify and statistically verify potential reasons that could explain this difference.

METHODS AND RESULTS

We identified 14 putative clinical, pathological and combined clinicopathological reasons that, altogether, could explain the phenomenon of the perceived greater diagnostic difficulty associated with MinSG tumours. We performed a comprehensive literature search and a statistical comparison of data from a large personal consultation series (biased for difficult cases) with cumulated data from straightforward, unselected (non-consultation) series from the literature. By performing this comparison, we identified, with statistical significance, a comprehensive series of reasons, as well as of consequences, of the greater difficulty in diagnosing MinSG tumours.

CONCLUSIONS

Among the 14 criteria, high frequencies of initial incisional biopsies and of a low-grade category in malignant tumours emerged as the two most important reasons for enhanced diagnostic difficulty. Very rare entities, unusual locations, shortcomings in clinicopathological communication, and pecularities of the special anatomical location of the hard palate, such as tumour necrosis, mucosal ulceration, pseudoinvasion, and the peculiar phenomenon of 'tumoral-mucosal fusion', contribute to further diagnostic difficulties. The awareness of these shortcomings and pitfalls enables us to provide a series of recommendations for clinicians and pathologists that might aid in assessment and reduce the rate of misdiagnosis of MinSG tumours.

Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.