Calcifying odontogenic cyst

Calcifying odontogenic cyst (COC) is a rare developmental lesion that comes from odontogenic epithelium. It is also known as a calcifying cystic odontogenic tumor, which is a proliferation of odontogenic epithelium and scattered nest of ghost cells and calcifications that may form the lining of a cyst, or present as a solid mass.

It can appear in any location in the oral cavity, but more commonly affects the anterior (front) mandible and maxilla. It is most common in individuals in their 20s to 30s, but can be seen at almost any age, regardless of gender. On dental radiographs, the calcifying odontogenic cyst appears as a unilocular (one circle) radiolucency (dark area). In one-third of cases, an impacted tooth is involved. Histologically, cells that are described as "ghost cells", enlarged eosinophilic epithelial cells without nuclei, are present within the epithelial lining and may undergo calcification.

Most calcifying odontogenic cysts appear asymptomatic. They are normally presented as a painless, slow-growing mass on the mandible and/or the maxilla, mostly in the front of the mouth. Symptoms include swelling in the mouth, both inside the bone, in the tooth bearing areas, and outside the bone, in the gingiva. When a COC is located in the maxilla, individuals might complain of nasal stiffness, epistaxis, and headache.

Impacted or displaced teeth are often found due to COC. The diameter of the cyst ranges from 2 to 4 cm and swelling pain may be present. Intrabony (between bone) expansions may produce hard bony expansion and may perforate cortical bones. It can also extend to soft tissue.

It is believed that the calcifying odontogenic cyst arose from odontogenic epithelial remnants (remains) that were trapped within the bones of the maxilla and mandible or gingival tissues. It is associated with impacted and unerupted teeth.

Calcifying odontogenic cyst can is the presence of a variable number of ghost cells within the epithelial lining. The eosinophilic ghost cells are those that have been changed in a way without a nucleus, but it has been able to maintain its basic cell shape.

The mechanism for the formation of a calcifying odontogenic cyst is controversial, whether the ghost cells change is based on coagulative necrosis (accidental cell death caused by ischemia or infarction)/the build up of enamel protein or it's a form of normal or abnormal keratinization (formation of keratin proteins) of odontogenic epithelium. Large amounts of ghost cells fuse together to form large sheets of material with an undefined shape and are acellular. Calcification of the sheets may occur. It first appears as fine basophilic granules that increase in size and number forming large masses of calcifying material. Eosinophilic dentinoid (abnormal form of dentin) material is present next to a sheet of ghost cells.

Some forms of the cystic type of COC, the epithelial lining proliferates into the lumen (inside space of the cyst) so its filled with masses of ghost cells and dystrophic calcifications.