The 4th edition of the World Health Organization's Classification of Head and Neck Tumours was published in January of 2017. This article provides a summary of the changes to Chapter 4 Tumours of the oral cavity and mobile tongue and Chapter 8 Odontogenic and maxillofacial bone tumours. Odontogenic cysts which were eliminated from the 3rd 2005 edition were included in the 4th edition as well as other unique allied conditons of the jaws. Many new tumors published since 2005 have been included in the 2017 classification.
The latest (4th) edition of the World Health Organization Classification of Head and Neck tumours has recently been published with a number of significant changes across all tumour sites. In particular, there has been a major attempt to simplify classifications and to use defining criteria which can be used globally in all situations, avoiding wherever possible the use of complex molecular techniques which may not be affordable or widely available. This review summarises the changes in Chapter 8: Odontogenic and maxillofacial bone lesions. The most significant change is the re-introduction of the classification of the odontogenic cysts, restoring this books status as the only text which classifies and defines the full range of lesions of the odontogenic tissues. The consensus group considered carefully the terminology of lesions and were concerned to ensure that the names used properly reflected the best evidence regarding the true nature of specific entities. For this reason, this new edition restores the odontogenic keratocyst and calcifying odontogenic cyst to the classification of odontogenic cysts and rejects the previous terminology (keratocystic odontogenic tumour and calcifying cystic odontogenic tumour) which were intended to suggest that they are true neoplasms. New entities which have been introduced include the sclerosing odontogenic carcinoma and primordial odontogenic tumour. In addition, some previously poorly defined lesions have been removed, including the ameloblastic fibrodentinoma, ameloblastic fibro-odontoma, which are probably developing odontomas, and the odontoameloblastoma, which is not regarded as an entity. Finally, the terminology \"cemento\" has been restored to cemento-ossifying fibroma and cemento-osseous dysplasias, to properly reflect that they are of odontogenic origin and are found in the tooth-bearing areas of the jaws.
The World Health Organisation classifications of tumours (often referred to as the 'Blue Book' series) provides the internationally recognised standard for diagnosis and research in neoplastic lesions. The 5th edition of the Classification of head and neck tumours,1 which will be published in 2022, updates current knowledge and integrates developing understanding of these conditions, including insights from molecular pathology techniques. There are several changes from the 4th edition (2017) which bring a more logical hierarchical classification, consensus definitions and provide greater insight into advances in our understanding of the pathogenesis of these varied lesions.2,3 Whilst there are 17 chapters in the 5th edition, covering different tumours and sites within the head and neck, this update will focus on the main changes of relevance to dental professionals working in primary and secondary care.
This article reviews the imaging features of head and neck lesions with updated 2017 World Health Organization (WHO) nomenclature. The major WHO changes include refined terminology of existing entities, descriptions of new tumor types, elimination of defunct categories, and updated biological characterization of various tumor types. In particular, the updates pertaining to the following conditions will be reviewed: tumors of the oral cavity and oropharynx, including HPV-positive or HPV-negative squamous cell carcinoma, small cell carcinoma; tumors of the hypopharynx, larynx, trachea, and parapharyngeal space, including nomenclature revisions for laryngeal neuroendocrine tumors; tumors of the nasal cavity and paranasal sinuses including newly added entities such as NUT carcinoma and biphenotypic sinonasal sarcoma; odontogenic and maxillofacial bone tumors, including the reversal of terminology for certain cystic lesions; tumors of the salivary glands, including updated terminology related to high-grade transformation and polymorphous adenocarcinomas tumors; temporal bone lesions including modifications of the nomenclature and classification criteria; tumor-like lesions of the neck and lymph nodes, with a discussion encompassing developmental cysts, metastases of unknown primary, and heterotopia-associated neoplasia; and mucosal melanoma. Familiarity with the proper WHO terminology for conditions that might be mentioned in differential diagnoses and a general understanding of the behavior of head and neck lesions can help optimize imaging assessment and reporting.
The combination of polymorphous low-grade adenocarcinoma and cribriform adenocarcinoma of the tongue and minor salivary glands under a single-term polymorphous adenocarcinoma (PAC) is the other important difference between new and the old WHO-HNT . This is a rare head and neck cancer, which generally has a good prognosis . However, PAC has nonspecific imaging features, which include occasional adjacent bony invasion and erosion, but otherwise smooth borders with a fibrous capsule that appears as a hypointense rim on T2-weighted images, as well as a progressive enhancement pattern (Fig. 2). Rather than provide a specific diagnosis, the main responsibility of the radiologist is to assess the local extent of the tumor and to identify potentially metastatic lymph nodes .
As opposed to metastases, heterotopia-associated carcinomas of the head and neck most commonly arise from ectopic salivary or thyroid tissue. For example, papillary thyroid carcinoma can arise from thyroglossal duct cysts (Fig. 14) . The ectopic tumors can display analogous imaging features to their counterparts in regular locations. However, imaging may not necessarily help differentiate heterotopic primary tumors from lymph node metastases, which is an important consideration and may require detailed histological examination in order to make such a distinction.
There are many types of developmental and acquired cysts included in the updated WHO section on tumor-like lesions of the head and neck, including thyroglossal duct cysts, branchial cleft cysts, inclusion cysts, foregut duplication cysts, and ranulas (Fig. 15). While all of these can appear as simple cysts on imaging, the location of the lesions, such as midline versus lateral neck, can help distinguish them. Furthermore, some of the tumor-like lesions can display specific features, such as fat components in dermoids and sinus tracts with branchial cleft cysts. In addition, some of these cysts can be complicated by rupture and infection, which can manifest as cyst wall thickening and surrounding inflammation, and in rare cases, there may be an underlying neoplasm [35,36,37,38].
Various tumor-like lesions of the head and neck. Axial CT image (a) shows a midline anterior neck thyroglossal duct cyst. Axial CT image (b) shows an infected left neck branchial cleft cyst with surrounding inflammation and a distended sinus (arrow) that extends towards the hypopharynx. Axial CT image (c) shows a ruptured fat attenuation dermoid in the left lateral periorbital region with surrounding inflammation. Axial fat-suppressed T2-weighted MRI (d) shows a midline oral cavity foregut duplication cyst. Axial fat-suppressed T2-weighted MRI (e) shows a cystadenocarcinoma of the left sublingual region (arrow) associated with a ranula
Cancers that are known collectively as head and neck cancers usually begin in the squamous cells that line the mucosal surfaces of the head and neck (for example, those inside the mouth, throat, and voice box). These cancers are referred to as squamous cell carcinomas of the head and neck. Head and neck cancers can also begin in the salivary glands, sinuses, or muscles or nerves in the head and neck, but these types of cancer are much less common than squamous cell carcinomas (1, 2).
If a squamous cell carcinoma of the head and neck is going to spread, it almost always does so locally and/or to the lymph nodes in the neck. Sometimes, cancerous squamous cells can be found in the lymph nodes of the upper neck when there is no evidence of cancer in other parts of the head and neck, possibly because the original primary tumor is too small. When this happens, the cancer is called metastatic squamous cell carcinoma with unknown (occult) primary. More information about this cancer type can be found in the Metastatic Squamous Neck Cancer with Occult Primary (PDQ) cancer treatment summary.
Researchers estimated that more than 68,000 men and women in the United States would be diagnosed with head and neck cancers in 2021 (31). Most will be diagnosed with mouth, throat, or voice box cancer. Paranasal sinus and nasal cavity cancer and salivary gland cancer are much less common.
Avoiding oral HPV infection can reduce the risk of HPV-associated head and neck cancers. In June 2020, the Food and Drug Administration granted accelerated approval of the HPV vaccine Gardasil 9 for the prevention of oropharyngeal and other head and neck cancers caused by HPV types 16, 18, 31, 33, 45, 52, and 58 in persons aged 9 through 45 years. More information about these vaccines is available in the Human Papillomavirus (HPV) Vaccines fact sheet.
Patients who receive radiation to the head and neck may experience side effects during and for a short while after treatment, including redness, irritation, and sores in the mouth; a dry mouth or thickened saliva; difficulty in swallowing; changes in taste; or nausea. Radiation may also cause loss of taste, which may decrease appetite and affect nutrition, and earaches (caused by the hardening of ear wax). Patients may also notice some swelling or drooping of the skin under the chin and changes in the texture of the skin. The jaw may feel stiff, and patients may not be able to open their mouth as wide as before treatment. 59ce067264