Benign odontogenic tumors

In 2017, the  4th edition of WHO classification of head and neck made various changes in the benign odontogenic tumors of jaw and the classification was made simpler than the previous one being used.

    Changes made in 2017 WHO classification:

    • Previously in 2005 classification the benign odontogenic tumors were divided the into “Odontogenic epithelium with mature, fibrous stroma without odontogenic ectomesenchyme, Odontogenic epithelium with odontogenic ectomesenchyme, with or without hard tissue formation, and Mesenchyme and/or odontogenic ectomesenchyme with or without odontogenic epithelium.” In 2017, only epithelial, mesenchymal (ectomesenchymal), and mixed odontogenic tumors are recognized making it simpler.
    • In the previous classification, Ameloblastomas were classified as solid/multicystic, extraosseous/peripheral, desmoplastic and unicystic types. Now the classification has been simplified and narrowed to ameloblastoma, unicystic ameloblastoma and extraosseous/peripheral types. The adjective “solid/multicystic” for the conventional ameloblastoma was eliminated due to the potential confusion with with unicystic ameloblastoma and lack of any specific biologic significance of using it.
    • Desmoplastic ameloblastoma was reclassified as histological subtype of ameloblastoma as it behaves similarly to conventional ameloblastoma.
    • The association of odontoma and ameloblastoma is well-known but the specific entity of odontoameloblastoma as called in 2005 classification was dropped and it is to be considered as ameloblastoma arising in odontoma
    • Keratocystic odontogenic tumor was classified back as a cyst known as odontogenic keratocyst
    • Calcifying cystic odontogenic tumor was reverted to calcifying odontogenic cyst
    • In 2017, the odontogenic fibroma was defined as  a rare neoplasm of mature fibrous connective tissue, with variable amounts of inactive-looking odontogenic epithelium with or without evidence of calcification.
    • Primordial odontogenic tumor, a new entity, was added in the 2017 classification
    • The benign odontogenic tumor; epithelial origin category includes the following tumors;
      • Ameloblastoma, conventional, unicystic, extra-osseus/peripheral type
      • Metastasizing ameloblastoma
      • Squamous odontogenic tumor
      • Calcifying epithelial odontogenic tumor
      • Adenomatoid odontogenic tumor

 

    1. Ameloblastoma

It is a benign but locally aggressive odontogenic tumor.

Clinical presentation:

    • It affects all age groups more commonly 30-50 years in without gender predilection.
    • It may arise from dentigerous cyst or may be associated with impacted tooth

Hisological features:

    • Resemble developing enamel organ
    • Peripheral palisade of columnar cells surrounding edematous epithelium that resembles stellate reticulum.
    • Histological variants including follicular, plexiform and acanthomatous are seen but these all have same behavior whereas the peripheral type behaves differently so it is kept in a distinctive type.
    • Unicystic ameloblastoma: Two subtypes are well known having good prognosis and rare recurrence with simple nucleation.
      • Luminal type:  simple cyst lined by ameloblastomatous epithelium
      • Intraluminal subtype: luminal proliferations of  the ameloblastomatous epithelium
      • Mural unicystic ameloblastoma: it has similar prognosis as conventional ameloblastoma. Some evidence of aggressive behavior is noted but still requires more investigation.
    • Metastasizing ameloblastoma: it is reshuffled in the benign caregory. It is defined as a histologically benign typical ameloblastoma which metastasises to distant sites. Both the primary lesion and the metastasis must have histological features of benign ameloblastoma.
    1. Primordial odontogenic tumor

      It is a new entity that has been added in the new classification. It is a benign tumour composed of odontogenic mesenchyme with loosely arranged fusiform or stellate fibroblasts resembling dental papilla.

    1. Squamous odontogenic tumor:

Clinical presentation:

    • Braod age range
    • Around 20% multiple
    • Location is alveolar process of jaw

Radiographic presentation:  Well-circumscribed radiolucency reaching the roots of teeth

Histological appearance:

    • Islands of well-differentiated squamous epithelium
    • Fibrous connective tissue stroma
    • Epithelial islands are round to oval with varying size and shapes

Treatment: Conservative treatment and recurrences are rare

    1. Adenomatoid odontogenic tumor

    Clinical presentation:

    • Usually is second decade of life
    • Location is maxilla
    • Associated with unerupted tooth

Radiographic presentation: resembles dentigerous cyst or keratocyst

Microscopic appearance:

    • Well-encapsulated
    • There is a cyst wall which is thickened by nodular masses of epithelium and matrix
    • These masses were composed of whorled nodules of spindled cells and columnar cells with polarized nuclei
    • Rosettes and duct-like tubular structures are seen
    • Eosinophilic amorphous material that can calcify

Treatment: conservative including enucleation and curettage. Recurrences are rare

6.Calcifying epithelial odontogenic tumor (Pindborg tumor)

Clinical presentation: occurs usually 40 years. The location is mostly mandibular premolar-molar region. It is a locally expansive tumor

Radiographically: variable. May be unilocular or multilocular radiolucencies, mixed radiolucent-radioopaque image or densly radioopaque lesion

Histologically:

    • Strands and sheets of polyhedral, eosinophilic epithelial cells
    • Eosinophilic hyaline matrix with staining characteristics of amyloid and stains with Congo red and Thioflavin-T stains.

Treatment: It  is treated aggressively like ameloblastoma as it is locally expansive tumor.

The mesenchymal and mixed benign odontogenic tumors will be discussed in following articles alongwith the classification, changes and important details of malignant odontogenic tumors

Dr Saadia Hafeez

 

 

 

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