Cysts of Jaw

They are divided into two main categories

    1. odontogenic cysts
    2. Non-odontogenic cysts

The cysts are mainly lined by nonkeratinized squamous epithelial lining and lack specific histological features. They are mainly named according to their location and radiological findings but the histopathological examination is get done for confirmation of the diagnosis to be a simple cyst as clinically diagnosed meaning exclusion of any carcinoma or early carcinomatous changes

Odontogenic cysts

These are further classified into two main categories:

    • Inflammatory:
      • Periapical cyst
      • Residual cyst
      • Paradental cyst
    • Developmental cysts:
      • Dentigerous cyst
      • Odontogenic cyst
      • Gingival cyst of newborn
      • Gingival cyst of adult
      • Eruption cyst (now considered to be variant of dentigerous cyst)
      • Lateral periodontal cyst
      • Glandular odontogenic cyst
      • Calcifying odontogenic cyst

Non-odontogenic cysts

    • Nasopalatine canal cyst
    • Median palatine cyst
    • Nasolabial cyst
    • Globulomaxillary cyst

Few of the cysts with specific histological features are discussed as below;

    1. Dentigerous cyst

It is defined as a cyst that originates from the crown of an unerupted tooth.

Clinical presentation:

Most of them are unilocular but sometimes can be multiloclar as well.

Complications:

Displacement of adjacent teeth, jaw expansion and neoplastic transformation to ameloblastoma

Radiographic presentation:

Unilocular lesions associated with impacted third molar tooth in most of the cases

Gross findings:

Cyst wall is usually thin and envelops the crown of the tooth if submitted as such with the impacted tooth.

Microscopic appearance:

    • Thin layer of stratified squamous epithelium
    • Usually minimal inflammation but moderate to intense inflammation in presence of capsular fibrosis

The ameloblastomatous transformation of the cyst has to be looked for and ruled out.

Treatment:

Complete excision with extraction of impacted tooth is curative

    1. Odontogenic keratocyst:

It is an important lesion with a specific histological appearance, clinical correlation to a syndrome and its aggressive nature. In recent past, it had been named as Keratocystic odontogenic tumor due to its aggressive and destructive nature and its recurrence but the name of odontogenic keratocyst was reverted in latest 4th edition of WHO classification of head and neck tumors  in 2017.

Clinical presentation:

    • Can be seen at any age but most often presents in patients aged between 10- 40 years.
    • It is more common in males.
    • Location is posterior mandible
    • It is associated with Nevoid basal cell carcinoma syndrome in approximately 5% of patients
    • Nevoid basal cell carcinoma syndrome : the most important components of it are medulloblastoma, multiple basal cell carcinoma on skin, multiple keratocysts, shortened metacarpals, ovarian fibromas, lymphatic mesenteric cysts, ovarian fibromas, rib and vertebral abnormalities

Radiographically:

well-defined unilocular or multilocular radiolucencies

Histologically:

    • Thin, flat stratified squamous epithelium without rete ridges
    • The epithelial lining is five to eight cells thick
    • The epithelial surface is corrugated and parakeratinized
    • Cuboidal to columnar basal cells with dark nuclei polarized away from the basement membrane
    • Daughter cysts are seen

Treatment:

Complete removal of lesion is necessary as they can recur in 60% of cases of incomplete removal

Genetic association:  Mutations in PTCH gene are seen

    1. Calcifying odontogenic cyst

It also had been named as calcifying cystic odontogenic tumor but in 4th edition was reverted back to original name of calcifying odontogenic cyst.

Clinical features:

It affects patients between broad age range without gender predilection with painless enlargement of mandible or maxilla. One third are associated with unerupted tooth.

Radiographically: Unilocular, well-defined radiolucencies

Histologically:

    • Epithelial lining with ameloblastic basal epithelial features showing distinct layer of palisaded and polarized basal cells with dark nuclei and an overlying loose layer that resembles stellate reticulum.
    • Pale, eosinophilic ghost cells that may be lying scattered or form a collection are seen within the epithelium, wall or lying in the lumen. This is the characteristic feature of this entity

Treatment: Enucleation and curettage. Recurrence is rare.

These were the worth mentioning cysts with the rest of cysts equally important in clinical, radiographic as well as treatment point of view but less distinctive characteristic histological features. The benign and malignant tumors of the jaw will be discussed in coming articles.

DR SAADIA HAFEEZ

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