Mandible & maxilla
General
WHO classification


Topic Completed: 2 November 2020

Minor changes: 16 November 2020

Copyright: 2004-2020, PathologyOutlines.com, Inc.

PubMed Search: WHO classification[TIAB] head and neck tumors[TIAB]

Kelly Magliocca, D.D.S., M.P.H.
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Cite this page: Magliocca K. WHO classification. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillawhoclassification.html. Accessed November 23rd, 2020.
Definition / general
  • This classification (WHO 2017) is applicable to tumors that occur throughout the head and neck, including the nasal cavity, paranasal sinuses, skull base, nasopharynx, hypopharynx, larynx, trachea, parapharyngeal space, oral cavity, mobile tongue, oropharynx, salivary glands, neck (including lymph nodes), gnathic maxillofacial bones and ear
Major updates
  • New entities:
    • Sclerosing odontogenic carcinoma: cytologically bland epithelial malignancy with stromal sclerosis exhibiting aggressive infiltrative growth into muscle and nerve; the infiltrating epithelial component tends to be small single file cords and strands which can be difficult to appreciate on routine sections and is best demonstrated with cytokeratin immunohistochemistry
    • Primordial odontogenic tumor: benign tumor composed of an immature variably cellular connective tissue resembling dental papilla or odontogenic ectomesenchyme; the tumor is surfaced by cuboidal to columnar epithelium resembling the inner enamel epithelium of the enamel organ
  • Renamed / refined entities:
    • Ameloblastic carcinoma: three subtypes of ameloblastic carcinoma listed in WHO 2005 collapsed into a single entity, ameloblastic carcinoma
    • Primary intraosseous carcinoma: collapsed the complex 2005 WHO classification of primary intraosseous carcinoma into a single entity, primary intraosseous carcinoma
    • Ameloblastoma: classification simplified to three types, ameloblastoma, unicystic ameloblastoma and extraosseous / peripheral types
    • Desmoplastic ameloblastoma: reclassified as a histologic subtype of ameloblastoma and not a unique clinicopathologic entity
    • Odontogenic fibromas: previously divided into a simple type (epithelium poor) and WHO type (epithelial rich); this distinction was eliminated and odontogenic fibroma is now defined as having variable amounts of inactive looking odontogenic epithelium with or without evidence of calcification
    • Cemento-ossifying fibroma: included in the 2017 classification under odontogenic tumors to distinguish it from the juvenile categories of ossifying fibroma
    • Keratocystic odontogenic tumor: renamed and reclassified as odontogenic keratocyst; the working group noted evidence currently lacking to justify the continuation of 2005 designation of keratocystic odontogenic tumor
    • Calcifying cystic odontogenic tumor: renamed and reclassified as calcifying odontogenic cyst in the absence of justification for classifying the lesion as neoplastic
  • Removed entities:
    • Odontoameloblastoma: now part of ameloblastoma
    • Ameloblastic fibro-odontoma and ameloblastic fibro-dentinoma: now recognized as falling within the spectrum of odontoma, therefore are now classified as odontomas
  • Reinstated entities:
    • Odontogenic carcinosarcoma included in the 2017 classification of malignant odontogenic tumors due to improved documentation confirming it as distinct
  • Notable updates:
    • Inclusion of a classification for gnathic epithelial lined cysts is notable; such a classification has not appeared in the WHO since 1992
    • Primordial cyst is not used synonymously with odontogenic keratocyst
    • Orthokeratinized odontogenic cyst is recognized as distinct from odontogenic keratocyst
    • Refined criteria for glandular odontogenic cyst presented
    • One nonodontogenic epithelial lined cyst included in the 2017 classification: nasopalatine duct cyst
WHO (2017)
Microscopic (histologic) images

Contributed by Kelly Magliocca, D.D.S., M.P.H.
Adenomatoid odontogenic tumor

Adenomatoid odontogenic tumor

Ameloblastic carcinoma Ameloblastic carcinoma

Ameloblastic carcinoma

Ameloblastic fibroma

Ameloblastic fibroma



Ameloblastoma

Ameloblastoma

Ameloblastoma, extraosseous / peripheral type

Ameloblastoma, extraosseous / peripheral type

Ameloblastoma, unicystic type

Ameloblastoma, unicystic type

Aneurysmal bone cyst

Aneurysmal bone cyst

Calcifying epithelial odontogenic tumor

Calcifying epithelial odontogenic tumor

Calcifying odontogenic cyst

Calcifying odontogenic cyst



Cemento-osseous dysplasia

Cemento-osseous dysplasia

Cementoblastoma

Cementoblastoma

Central giant cell granuloma

Central giant cell granuloma

Cherubism

Cherubism

Chondrosarcoma

Chondrosarcoma

Clear cell odontogenic carcinoma

Clear cell odontogenic carcinoma



Dentigerous cyst

Dentigerous cyst

Dentinogenic ghost cell tumor

Dentinogenic ghost cell tumor

Desmoplastic fibroma

Desmoplastic fibroma

Fibrous dysplasia

Fibrous dysplasia

Gingival cyst

Gingival cyst

Glandular odontogenic cyst

Glandular odontogenic cyst



Inflammatory collateral cysts

Inflammatory collateral cysts

Lateral periodontal cyst

Lateral periodontal cyst

Melanotic neuroectodermal tumor of infancy

Melanotic neuroectodermal tumor of infancy

Nasopalatine duct cyst

Nasopalatine duct cyst

Odontogenic fibroma

Odontogenic fibroma

Odontogenic keratocyst

Odontogenic keratocyst



Odontogenic myxoma / myxofibroma

Odontogenic myxoma / myxofibroma

Odontogenic sarcomas

Odontogenic sarcoma

Odontoma

Odontoma

Orthokeratinized odontogenic cyst

Orthokeratinized odontogenic cyst

Ossifying fibroma

Ossifying fibroma

Osteoma

Osteoma



Osteosarcoma, NOS

Osteosarcoma, NOS

Peripheral giant cell granuloma

Peripheral giant cell granuloma

Primary intraosseous carcinoma, NOS

Primary intraosseous carcinoma, NOS

Primordial odontogenic tumor

Primordial odontogenic tumor

Radicular cyst

Radicular cyst



Simple bone cyst Simple bone cyst

Simple bone cyst

Solitary plasmacytoma of bone

Solitary plasmacytoma of bone

Squamous odontogenic tumor

Squamous odontogenic tumor

Board review style question #1

Which new benign entity has been added in the 2017 WHO classification of odontogenic and maxillofacial bone tumors?

  1. Adenomatoid odontogenic tumor
  2. Ameloblastic carcinoma
  3. Primordial odontogenic tumor
  4. Sclerosing odontogenic carcinoma
Board review answer #1
C. Primordial odontogenic tumor. Primordial odontogenic tumor is a recently recognized benign odontogenic tumor. Being exceptionally rare in the lung, it was introduced in the 2015 WHO classification of lung tumors. Adenomatoid odontogenic tumor is a benign odontogenic tumor in the WHO classification but is not a new entity in the 2017 edition. Sclerosing odontogenic carcinoma is a new entity in the 2017 WHO but is malignant. Ameloblastic carcinoma is an odontogenic malignancy and is not a new entity in the 2017 edition.

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Reference: WHO Classification of Odontogenic and Maxillofacial Bone Tumors
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