It has been over a decade since the last iteration of the World Health Organization (WHO) classification of head and neck tumors (the so called “blue book”). This time interval has brought several key changes to a broad variety of tumor types in the head and neck region to the point that the topic of envisioning future changes in the WHO was a focus of a North American Society of Head and Neck Pathology Companion Meeting, March 2, 2014, in San Diego, California [1–6]. Thus, the 4th edition of the WHO blue book is a crystallization of many of these predicted changes, and a welcome update.
As with other organ sites, the (informal) guiding principles of this edition include:
Utility as a quick, efficient reference or field guide for pathologists as well as clinicians involved in head and neck cancer care.
Suitability for a wide variety of international practice settings ranging from subspecialized academic universities to under-resourced community practices.
Avoidance of an overemphasis on rare, poorly defined entities and occurrences.
A conservative approach to controversial topics and provisional entities.
Standardization of nomenclature when possible and harmonization with other organ site classification schema.
As expected, the major changes include refinement of existing entities, description of new tumor types, collapse/removal of defunct categories, and an update on the biology of various tumor types. Classic clinicopathologic variables as well as newer ancillary (including molecular) findings are included with each of the entities, but kept within practical limits. Somewhat serendipitous is the fairly close alignment of this edition with the recent release of 8th edition of the AJCC staging manual [7] which has allowed some harmonization of terminology.
By far the most significant and long awaited change to this edition is the recognition of oropharynx as a distinctive subsite. This facilitates the recognition of the most significant advance in head and neck cancer over this time interval, namely the recognition of human papillomavirus related squamous cell carcinoma as a distinct clinicopathologic entity, which closely aligns with the new and distinct staging for this tumor type as per AJCC. Other major changes involve description of several new entities in the sinonasal tract, salivary gland, as well as introduction of a new chapter on tumors and tumor like lesions of the neck.
In light of this much anticipated edition, the Head and Neck Pathology Journal is pleased to assemble an international panel of experts, most of whom were authors of several of the chapters and at the meeting in Lyon. As the guest editor for this special issue, I have had the distinct privilege of working this esteemed group of pathologists. Drs. Bishop and Stelow will review the changes and updates in tumors of the nasal cavity, paranasal sinuses, and skull base, and introduce new entities such as NUT carcinomas, and HPV-related carcinoma with adenoid cystic–like features. Drs. Stelow and Wenig discuss tumors of the nasopharynx with a focus on nasopharyngeal carcinoma and some of the newer data on tumor biology. Drs. Gale, Poljiak and Zidar discuss updates in tumors of the hypopharynx, larynx, trachea, and parapharyngeal space, emphasizing grading of dysplasia in precursor lesions as well as nomenclature revisions for laryngeal neuroendocrine tumors. Dr. Muller summarizes the recent changes in tumors of the oral cavity, from the mundane, namely squamous cell carcinoma to the more obscure such as ectomesenchymal chondromyxoid tumor. Drs. Lewis and Westra outline the new addition to the tumor classification, namely tumors of the oropharynx, with an emphasis on the critical recognition of HPV related squamous cell carcinoma. Drs. Katabi and Lewis describe yet another new addition, tumors and tumor-like lesions of the neck and lymph node, with a discussion spanning developmental cysts, metastases and heterotopia associated neoplasia. Drs. Seethala and Stenman summarize updates in tumors of salivary gland, focusing on the impact of defining translocations, concepts of high grade transformation, as well as the controversial topics of nomenclature for polymorphous adenocarcinomas. Drs. Wright and Vered summarize the changes in odontogenic and maxillofacial bone tumors, discussing the reversal of terminology for select cystic lesions and providing a nuanced discussion of the context surrounding this.
Dr. Thompson discusses tumors of the ear. Drs. Williams and Tischler summarize advances in the biologic understanding and terminology for paraganglion tumors, addressing harmonization with the upcoming WHO classification of endocrine tumors. While not a specific chapter, Drs. Brown and Elenitoba-Johnson provide an update on hematolymphoid neoplasms from each section. Similarly, Dr. Williams summarizes the updated features of melanocytic lesions for each section.
We hope that this special issue provides a preview and summary of this key reference for pathologists encountering both rare and common head and neck tumors.
Compliance with Ethical Standards
Disclosures
The authors declare that they have no conflict of interest.
Footnotes
Special Issue: World Health Organization Classification Update
References
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