News in the 5th edition of the WHO Classification of Tumours of the Head and Neck: Tumours of the Sinonasal Tract and Skull Base Tumors.

The World Health Organization (WHO) recently published the 5th edition of head and neck tumors. This edition describes both existing entities and a group of emerging entities, along with updates regarding taxonomy and detailed characteristics of tumors and tumor-like lesions. Sinonasal tumors and skull base tumors represent a heterogeneous group of tumors with significant histological variability and overlap in imaging methods. An important change in the 5th edition of the WHO classification is the relocation of recurrent soft tissue, hematolymphoid, and neuroectodermal tumors into a separate chapter, meaning they are no longer repeated in other chapters as they were previously. Only those tumors that are unique to the sinonasal area remain classified in this chapter. In this review article, we will primarily provide a brief overview of all 24 diagnostic entities, allowing readers to gain a concise understanding. We will focus in detail on the new entities of SWItch/Sucrose Non-Fermentable complex-deficient sinonasal carcinomas and human papillomavirus-related multiphenotypic sinonasal carcinoma. In another review article in this issue, we detailed IDH-mutated sinonasal malignancies; therefore, we will exclude them from this overview and concentrate on DEK::AFF2 carcinomas, currently classified as sinonasal undifferentiated carcinomas or non-keratinizing squamous cell carcinomas, respectively.