Salivary gland cancer: new classifications and diagnostic challenges

Salivary gland cancer: new classifications and diagnostic challenges

Royal College of Pathologists publishes new dataset for reporting salivary gland tumours

The diagnosis of salivary gland cancer is complicated by the large number of benign and malignant tumours that can look similar under a microscope. Recently, the Royal College of Pathologists (RCPath) has updated its guidance for reporting salivary gland cancers (1) following publication of the 5th edition of the World Health Organization (WHO) classification of Head and Neck Tumours (2). Key points in the guidance include new types of tumour, how tumours are graded, the extent of tumour invasion, the stages of cancer (pathological staging), and additional methods used for diagnosis.

Background

The WHO has classified 15 benign and 21 malignant tumour types within the salivary glands (2). Over the past decade, the classification system has undergone significant revisions, incorporating molecular-level definitions for some tumours. With more than ten years having passed since RCPath last updated its dataset on this topic, it was time to align it with current advancements in the field. RCPath datasets play a crucial role in standardising cancer reporting practices among pathologists, defining acceptable standards for handling pathology specimens, and ultimately improving the accuracy of cancer diagnosis and treatment (3).

Professor Ali Khurram, Hannah Crane and Mollie Clark from the School of Clinical Dentistry, University of Sheffield, have published an insightful overview of the updated RCPath dataset, focusing on new concepts and emerging controversies. Professor Khurram also served as a lead author on the recently released RCPath dataset for salivary gland cancers. The authors note that currently available treatments for salivary gland tumours that have returned, or those that are inoperable or have spread elsewhere in the body, are highly limited and have low efficacy.

Molecular alterations and testing

An improved understanding of common molecular alterations within these difficult-to-treat tumours has the potential to reveal new opportunities for targeted therapy. For example, the discovery of a molecular alteration that is present in over half of all adenoid cystic carcinomas, which are notoriously difficult to treat, could provide pathologists with advance warning of the type of cancer they are dealing with and point to a possible target for future treatments (4).

Molecular testing has been a useful addition to the diagnostic toolbox and can reveal a lot more about a tumour than just looking down a microscope. But overreliance on the technology is unwise; a negative result doesn’t necessarily rule out a diagnosis (5).

Other drawbacks to molecular testing, particularly in developing countries, include cost, availability and turnaround time (1). In the case of lung cancer, for example, a global survey revealed that a turnaround time of more than 10 days for molecular testing is typical (6), leading to delays in both clinical decision making and treatment. Khurram and colleagues warn that, as molecular testing becomes more widespread in salivary gland pathology, it will be important to develop standard procedures and education globally (1).

Lastly

The latest RCPath dataset provides a summary of the current understanding of salivary gland cancers and highlights areas where further research is needed. Obstacles to optimal research still exist due to the rarity of many tumours, making it difficult to establish large enough study groups and access to tissue samples. Collaboration and sharing of knowledge and resources are key to overcoming these barriers. An increased understanding of factors that predict the course of disease will hopefully lead to better care and outcomes for patients with these rare tumours.

References

1. Crane H, Clark M, Khurram SA. Update on the dataset for histopathological reporting of salivary gland carcinomas: current concepts and controversies in salivary gland pathology. Diagn Histopathol [Internet]. 2025; Available from: https://doi.org/10.1016/j.mpdhp.2025.02.001
2. Skalova A, et al. Salivary gland tumours. In: WHO classification of head and neck tumours. 2024. p. 159–252.
3. RCPath. Cancer datasets and tissue pathways. Available from: https://www.rcpath.org/profession/guidelines/cancer-datasets-and-tissue-pathways.html
4. Xu B, et al. Predictors of outcome in adenoid cystic carcinoma of salivary glands: a clinicopathologic study with correlation between MYB fusion and protein expression. Am J Surg Pathol. 2017;41:1422–32.
5. Moutasim K, Thomas G. Salivary gland tumours: diagnostic challenges and an update on the latest WHO classification. Diagn Histopathol. 2020;26:159–64.
6. MO Smeltzer, et al. The international association for the study of lung cancer global survey on molecular testing in lung cancer. J Thorac Oncol. 2020;15:1434–48.

Last updated May 2025