Activating IGF1R hotspot non-frameshift insertions define a novel, potentially targetable molecular subtype of adenoid cystic carcinoma

New Entities and Concepts in Salivary Gland Tumor Pathology: The Role of Molecular Alterations

CONTEXT.—

Salivary gland tumors are rare tumor types for which the molecular understanding has resulted in a rapid expansion and shuffling of entities. These changes are reflected in the 5th edition World Health Organization Classification of Head and Neck Tumours (WHO 5th edition), although many nuances still remain.

OBJECTIVE.—

To review how molecular alterations have helped recategorize, justify, and reinstate entities into our lexicon as well as defining interrelationships between categories, new entities, and subtypes. Furthermore, newer theranostic applications to molecular phenotype will be summarized.

DATA SOURCES.—

World Health Organization Classification of Head and Neck Tumours (WHO 3rd through 5th editions), literature review, and personal and institutional experience.

CONCLUSIONS.—

Molecular alterations have helped reclassify, retain, and create new categories by augmenting rather than replacing standard criteria. Key entities that have emerged include sclerosing polycystic adenoma, microsecretory adenocarcinoma, and mucinous adenocarcinoma. Molecular phenotypes solidify the range of morphology in established entities such as mucoepidermoid carcinoma and facilitate connectivity between entities. Molecular characteristics now allow for targeted therapeutic approaches for secretory carcinoma and adenoid cystic carcinoma.

The Therapeutic Landscape of Salivary Gland Malignancies-Where Are We Now?

Salivary gland malignancies (SGMs) account for less than 5% of new diagnoses in head and neck tumors. If feasible, surgery is the preferred treatment modality. Nevertheless, some malignancies have a tendency of recurrence, with possible distant metastasis. Alternative treatment strategies, such as primary radiation or chemotherapeutics, often present low response rates. As a result, there is an unmet need for novel therapeutic approaches. Nowadays, target-based therapies (e.g., small inhibitors and immunotherapy) are used by the medical oncologist for possible treatment of advanced SGMs. Based on recent published trials, some novel treatments may provide additional disease control for some patients. However, sample sizes are small, the general findings are unsatisfactory, and a lot of uncertainties remain to be elucidated. Nevertheless, research shows that patients do not benefit from blind administration of systemic treatments and therefore a more personalized approach is highly needed. The aim of this review paper is to summarize the most recent advances in the biological understanding and molecular pathways of salivary gland cancers, the association of these pathways with the current treatments used and their implications for more personalized targeted-based therapies.