Ⅰ. INTRODUCTION
Odontogenic keratocyst (OKC), also known as keratocystic odontogenic tumor (KCOT), is a distinct clinicopathologic lesion that can be clearly identified by its histological characteristics. Clinically, OKC is characterized by a high recurrence rate (15-35%), an aggressive, destructive nature, and the presence of squamous epithelium1).
Plain radiography depicts OKC as a unilocular or multilocular lesion that is almost invariably scalloped with welldefined radiolucency. OKC has definite histopathological characteristics. Lesion epithelial linings show stratified squamous epithelium with a corrugated para-hyperkeratotic layer eight to ten cells thick, and basal cells of the epithelial lining exhibit a palisading pattern without rete peg formation2). However, hard tissue deposits such as dystrophic calcifica-tions, cartilage, hyaline bodies, and dentinoid have occasionally been reported in the connective tissue walls of OKC3).
Hence, we present the case of a 47-year-old man with OKC of the right maxillary sinus with calcification deposits and a review of related literature.
Ⅱ. CASE REPORT
A 47-year-old male patient visited the Department of Oral and Maxillofacial Surgery at Pusan National University Dental Hospital (Yangsan, South Korea) in March 2019 for inflammation in the left maxillary sinus. He had no relevant medical history. Clinical findings showed swelling on left maxillary gingiva and pus discharge with pain.
Orthopantomography (OPTG) and Cone Beam Computed Tomography (CBCT) showed full opacification with calcification and lateral wall resorption in the left maxillary sinus (Fig 1, 2). Findings of calcified materials and bony destruction of the sinus wall raised suspicion of a fungal infection. To evaluate the lesion further, facial CT with contrast enhancement was conducted. Enhancement revealed defects connecting the left maxillary alveolar process to the posterolateral wall of the left maxillary sinus (Fig 3).
The provisional diagnosis was aspergillosis infection, which manifests as either an invasive or non-invasive type and is related to an immunocompromised status. Since the prognosis and treatment of these two types differ, it is important to reach a differential diagnosis. Furthermore, early diagnosis is vital as any delay in the initiation of treatment can be life-threatening, regardless of infection type.4,5)
We immediately planned surgery under general anesthesia, and during surgery, we observed buccal bone perforation of maxilla and a multilocular cystic lesion containing yellowish fluid and a calcified mass (Fig 4). A specimen was sent for histological examination to the Department of Pathology, Pusan National University Yangsan Hospital, and the 5.6 x 3.5 x 1.0 cm sized mass was subjected to gross examination (Fig 5). Microscopic examinations showed a flat, epitheliumconnective tissue interface with a parakeratinized corrugated surface. A specimen showed hyperchromatic palisading basal cells and a lack of rete pegs. However, the calcification observed by radiography and gross examination was not observed by histological examination. Nevertheless, based on the histopathologic findings, odontogenic keratocyst (OKC) was diagnosed(Fig 6). At 6 months postoperatively, CBCT findings revealed no evidence of recurrence(Fig 7).
Written consent was received from the patient for the publication and use of medical data, and the study was approved by the institutional review board of Pusan National University Dental Hospital (PNUDH-2020-028).
Ⅲ. DISCUSSION
Odontogenic keratocyst (OKC) was first described by Phillipsen in 1956 and has undergone conceptual and terminological changes over recent decades. In 2005, it was classified as a tumor by World Health Organization (WHO), but in 2017, WHO in its classification of odontogenic lesions reverted to the earlier name, OKC6,7). OKC is believed to originate from dental lamina and occurs most commonly in the mandible ramus regions and posterior body. It shows maxilla and sinus involvement in ~25%, but fewer than 1% of diagnoses are made at these sites8). The distinctive clinical features of OKC include local destruction and tendency toward multiplicity. OKC reportedly has a high recurrence rate of between 25% and 60%. OKC is often asymptomatic, incidentally discovered on X-ray. But we present a case with rapid expansion and pain, and bone destruction to the lateral wall of the maxillary sinus and orbital floor. This is thought to be a clinical features of unusual OKC.
Although uncommon, hard tissue formation due to calcifications, such as dentinoid and cartilage may occur in the epithelial lining of OKCs3). Calcification in the form of dentinoid is extremely rare. The pathogenic mechanism of calcification in parts of the connective tissue walls is undetermined. Incomplete mineralization of calcium phosphate yields a globular appearance and short tubules are observed at the mass periphery, which suggest a calcification of a dentinoid nature6). Browne et al. reported high prevalences of whitlockite, inorganic phosphates, crystalline calcium phosphates, and hydroxyapatite in the aspirated fluid of some OKCs, which may explain the increased frequency of calcific deposits observed in cystic walls9). Structures found in epithelium or of hematogenous origin are Rushton bodies, nevus cells, and sweat glands, which may cause dystrophic calcification in the linings of OKCs at a rate of 4.6-11%. These structures may be linear, curved, or hairpin shaped.
Calcifications were also seen in our case and are a comparatively unusual finding. Unfortunately our histological examination failed to reveal any sign of calcification, so the characteristic of calcification could only be diagnosed with radiographic examination. Orthopantomography (OPTG) and Cone Beam Computed Tomography (CBCT) showed full opacification with irregular shped calcification and lateral wall resorption in the left maxillary sinus.
Ⅳ. CONCLUSION
The importance of calcified material formation in the biological behavior of OKCs is not clear. The prognosis of OKC has not been studied, and the relationship between the presence of calcification and the incidence of recurrence is unclear. We suggest a study be conducted to evaluate the correlation between the presence of calcified materials and recurrence.
