Calcifying Odontogenic Cyst Associated with Impacted Mandibular Canine: A Case Report

ARTICLE INFO


Introduction:
The calcifying odontogenic cyst (COC), also known as "Gorlin cyst", is an uncommon developmental odontogenic lesion, which was first introduced by Gorlin in 1962. (1) The fourth edition of the World Health Organization (WHO) Classification of Head and Neck Tumors (2017) retitled and reclassified this lesion as an odontogenic cyst; this lesion had been categorized in 2005 as an odontogenic tumor. (2) The COC is a rare developmental odontogenic cyst. It is assessed that COC accounts for less than 1% of all odontogenic cysts of the jaws. (3) It is associated with an impacted tooth in approximately one-third of cases. (4) In radiographic views, COCs may be seen as a unilocular and well-defined radiolucency with or without radiopacities resembling uneven calcifications or tooth-like structures. (5) sent with severe mobility of the mandibular anterior teeth. The patient complained of a headache without any history of local trauma or abnormal conditions. The medical history was unremarkable, and the patient was not taking any specific medication.
Cone-beam computed tomography (CBCT) scans were taken to examine the lesion in detail. On the reformatted panoramic image, a large unilocular cystic radiolucency, extending from the mesial aspect of the mandibular left first molar to the mesial aspect of the right first molar, with the transverse dimension of 39 mm was noted with significant root displacement of all the teeth involved with the lesion. Apical root resorption was detected in right and left first premolars, central and lateral incisors, right canine, and right second premolar ( Figure 2).
The axial sections demonstrated a large, well-defined, unilocular, radiolucent, and expansile lesion involving the area between the right and left first molars, measuring approximately 33 mm anteroposteriorly and 44.7 mm mediolaterally, with thinned buccal and lingual cortical plates and discontinuity of the buccal cortices in the area of the left lateral incisor and impacted canine (      The sagittal sections showed extension of the lesion with the largest dimension of 36.7 mm anteroposteriorly up to 34.2 mm superoinferiorly, containing multiple small radiopaque foci. Involvement of the inferior alveolar canal (IAC) by the lesion was detected ( Figure  6).
The radiological differential diagnoses included COC, dentigerous cyst, ameloblastic fibro-odontoma (AFO), adenomatoid odontogenic tumor (AOT), and calcifying epithelial odontogenic tumor (CEOT). Surgical resection was performed under general anesthesia (Figure 7). The surgical specimen was fixed in formalin and processed. The histopathological findings revealed a lesion with an outer layer of the odontogenic epithelium of variable thickness and a basal layer of ameloblast-like cells and stellate reticulum-like cells in the suprabasal layers. Ghost cells with calcifications were also seen in the epithelium. The histopathological examination supported the diagnosis of COC (Figure 8).

Discussion:
The COC is an uncommon lesion in the oral cavity lined by the odontogenic epithelium of variable thickness containing focal ghost cells, (4) which most frequently occurs in the incisor and canine region, with an approximately equal frequency within the maxilla and the mandible. (6) Asymptomatic swelling is a frequent presentation in extraosseous and intraosseous locations with an expansion of the buccal and/or lingual cortical plates. (7) The COC is usually an incidental radiographic finding, appearing as a unilocular or multilocular well-defined radiolucency, which may contain small irregular calcified bodies associated with an odontoma or an unerupted tooth. COCs are often located in the periapical or lateral periodontal areas. (8) Root resorption of the associated teeth has been observed in about 75-77% of the cases. (6) In 1991, Buchner categorized COC as peripheral and central COC based on

Figure 8: Histopathological sections of the lesion revealed an outer layer of the odontogenic epithelium of variable thickness and a basal layer of ameloblast-like cells and stellate reticulum-like cells in the suprabasal layers.
Ghost cells with calcifications were also seen in the epithelium. clinical features. The COC was further subclassified into cystic and neoplastic variants. The rare malignant variant of the COC was also entered into the classification. (7,9) The fourth edition of the WHO Classification of Head and Neck Tumors (2017) retitled and reclassified this lesion as an odontogenic cyst. (2) COCs are generally unilocular although 5-13% of cases are multilocular. Radiopaque bodies are seen in about 50% of COCs. This lesion may have a regular outline with well-demarcated margins. Early tumors may appear completely radiolucent. With maturation, they develop calcifications and may show a mixed radiolucent-radiopaque appearance. (1 0) In 20% of cases, COC is associated with odontomas and ameloblastomas. (11) The COC is a pathology that may be associated with impacted teeth. (12) Mortazavi and Baharvand reported COC as the least common pathology associated with impacted teeth. (13) It has also been reported that COC is often associated with anterior impacted teeth, (14) similar to the location of the COC in the present case report. However, the displacement of the adjacent teeth, as observed in the present case, has been rarely reported. (15) According to its radiographical appearance, COCs are most frequently in differential diagnosis with the dentigerous cyst, AFO, AOT, and CEOT. Considering that, in the present case report, the lesion surrounded the entire crown and root of the impacted tooth, a dentigerous cyst can be discounted. It is uncommon for COCs to appear in locations where AFOs or CEOTs commonly arise (the posterior mandible). However, this would not exclude AOTs because the incisorcanine-premolar region is the usual area involved in both jaws by AOTs and they may be associated with an impacted tooth. It may be difficult to radiographically differentiate AOTs from COCs. (16,17) Histologically, COCs are defined as cystic proliferation with a fibrous connective tissue surrounded by the od-ontogenic epithelium. The characteristic sign for COCs is the presence of ghost cells with nuclear remnants and calcifications. Enucleation is the treatment of choice for intraosseous COCs. The extraosseous COC is treated with surgical excision. The recurrence rate is low with a good long-term prognosis. (3)

Conclusion:
Although infrequent, COCs are often associated with impacted teeth and should be included in the differential diagnosis of jaw lesions. Oral and maxillofacial radiologists and surgeons should be careful with radiolucencies associated with impacted teeth because they have different effects on the surrounding structures and require different treatment plans, depending on the type of the lesion.