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Salivary Gland Cytopathology and Histopathology: Practical Insights and Updates From the World Health Organization Classification

Holmes, Brittany J. MD

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doi: 10.1097/PCR.0000000000000407
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“So many options in one little gland!” As a colleague quipped recently regarding a puzzling fine-needle aspiration (FNA), the field of salivary pathology frequently poses diagnostic challenges. With the publication of the latest World Health Organization Classification of Head and Neck Tumors, the number of distinct entities continues to expand. In tandem, our understanding of the molecular pathogenesis of salivary neoplasms is growing. This knowledge has generated a host of new immunohistochemical, cytogenetic, and molecular assays that can play a key role in supporting a morphologic diagnosis. However, optimal utilization of these tests requires judicious selection and shrewd interpretation—skills that are difficult to acquire because of the relative rarity of these tumors.

This issue of AJSP: Reviews and Reports is dedicated to equipping pathologists with knowledge, tools, and strategies for tackling the cytologic and histologic diagnosis of salivary lesions. The topics encompass newly defined tumors, rare but prognostically critical findings, and established neoplasms and nonneoplastic processes that cause diagnostic dilemmas. The authors bring a wealth of practical, accessible insights for handling these complex cases.

First, Drs Wong and Krane provide a thoughtful approach to common differential diagnostic conundrums in salivary cytology. By describing the strategic utility of ancillary studies, the authors explain the value, limitations, and efficient use of immunohistochemistry and fluorescence in situ hybridization in FNA material.

Building on these insights, Dr Rossi and colleagues detail the cytologic and histologic features of the newest additions to the World Health Organization classification, such as secretory carcinoma and clear cell carcinoma. While definitive diagnosis on FNA is challenging for these novel tumors, the authors highlight the unique morphologic, immunophenotypic, and cytogenetic findings of each entity.

Turning to the spectrum of oncocytic lesions, Drs Centeno and Wenig elucidate why oncocytic FNAs are difficult to categorize and how various classification systems approach this subject. The authors summarize the distinguishing cytomorphologic and histologic features of each oncocytic entity to help readers navigate this differential diagnosis.

Beyond morphologic challenges, Dr van Zante and colleagues offer a thoughtful discussion on implementing the Milan System for Reporting Salivary Gland Cytopathology. In addition to highlighting the advantages of standardized reporting, the authors point out caveats to consider. By focusing on how to maximize the value and accuracy of the cytopathology report for patient care, the authors contextualize standardized reporting as a tool in achieving this goal.

Dr Nakaguro and colleagues shed light on the infrequent but prognostically important finding of high-grade transformation in salivary carcinomas. After defining the best terminology for reporting purposes, the authors summarize current knowledge regarding the pathogenesis of this phenomenon. The morphologic features of high-grade transformation in each of the most common tumor types are reviewed and illustrated with practical tips for accurate classification.

Lymphoid lesions of the salivary glands can be daunting for nonhematopathologists. Drs Lubin and Lin provide a straightforward and practical guide to FNA features of lymphomas in the major salivary glands. Additionally, they describe how to distinguish lymphomas from nonneoplastic mimics.

Finally, Dr Hernandez-Prera systematically reviews nonneoplastic inflammatory diseases that form masses in the salivary glands. Frequently overlapping clinically with neoplasms, sialadenitis represents a spectrum of infectious, autoimmune, and mechanical processes. This well-illustrated discussion equips readers to recognize the clinical context and pathologic features that characterize distinct types of sialadenitis.

We are grateful to each of the authors for sharing their expertise on these wide-ranging, relevant topics. Their contributions will enrich your understanding and enable you to manage salivary cases with greater confidence and skill.

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