Calcifying Odontogenic Cyst

Calcifying odontogenic cyst is a rare developmental odontogenic cyst, lined by ameloblast like epithelium and containing ghost cells that often calcify. It makes up under 1% of odontogenic cysts and occurs in two age peaks, in the second and in the sixth decades.

The lesion is found equally in the maxilla and mandible and most often in the incisor and canine region. About a quarter to a half of cases are associated with an odontoma or other odontogenic lesion, and it is often linked to an impacted tooth.

Pathophysiology. Ghost cells are swollen eosinophilic epithelial cells that have lost their nuclei but kept their outline, and they accumulate and undergo dystrophic calcification and dentinoid formation.

Mutations in the beta catenin gene (CTNNB1) have been shown in many cases. A solid variant (dentinogenic ghost cell tumour) is a neoplasm and behaves more aggressively.

Slow, painless swelling of the jaw or gingiva, often found on a radiograph taken for an unerupted tooth. Peripheral lesions present as a firm gingival mass. Cortical expansion, displacement of teeth and delayed eruption occur.

Pain or discharge suggests secondary infection. Large lesions can resorb the roots of neighbouring teeth.

• Panoramic radiograph or periapical film: a well defined unilocular, occasionally multilocular, radiolucency, with radiopaque flecks of calcified ghost cells in a proportion of cases, and root divergence or resorption. A mixed lucent and opaque appearance is typical.
• Cone beam CT for extent, the relation to impacted teeth and odontoma, and surgical planning.
• Incisional or excisional biopsy with histology: cyst lining of columnar basal cells resembling ameloblasts, an overlying layer of loosely arranged stellate reticulum like cells, ghost cells, and dentinoid deposition. Confirm the absence of a solid ameloblastoma like component.
• Immunohistochemistry for nuclear beta catenin is supportive and not routine.

Differential diagnosis.

• Dentigerous cyst and radicular cyst
• Odontogenic keratocyst
• Adenomatoid odontogenic tumour
• Calcifying epithelial odontogenic tumour
• Complex odontoma and ameloblastic fibro odontoma
• Unicystic ameloblastoma
• Dentinogenic ghost cell tumour

• Enucleation with curettage, with removal of any associated odontoma or impacted tooth when needed. Recurrence is uncommon, below 5%.
• Large cysts near vital structures: decompression for 6 to 12 months before enucleation.
• Solid or aggressive variant (dentinogenic ghost cell tumour), or lesions with a solid component on histology: wide local excision with a margin of 1 cm of normal bone and reconstruction, because recurrence is higher after conservative treatment.
• Peripheral lesions: local excision with a gingival margin of normal tissue.
• Antibiotics only for infection with spread: amoxicillin 500 mg orally three times daily for 5 days (reduce to 500 mg every 12 hours at eGFR 10 to 30), or clindamycin 300 mg four times daily in penicillin allergy.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.
• Surgical orthodontic management of impacted teeth if they are preserved.

Special groups. Multiple or familial lesions need assessment for Gorlin syndrome and other syndromes, with attention to keratocysts, skin basal cell carcinoma and skeletal anomalies.

Monitoring. Radiographs at 6 and 12 months, then annually for at least 5 years because late recurrence has been reported.

Referral and escalation. Refer to oral and maxillofacial surgery for biopsy and treatment. Urgent referral for a rapidly growing, destructive lesion, solid tumour features on histology or multiple lesions.