Contemporary Clinical Dentistry

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 11  |  Issue : 1  |  Page : 20--27

Imaging characteristic of 11 lesions of odontogenic keratocyst in the indian subpopulation: A cone-beam computed tomography experience


Shilpa Padar Shastry1, Padma Pandeshwar1, S Padmashree1, N Naveen Kumar1, Swati Garg1, CJ Sanjay2,  
1 Department of Oral Medicine and Radiology, Vydehi Institute of Dental Sciences and Research Centre, Bengaluru, Karnataka, India
2 Department of Oral Medicine and Radiology, JSS Dental College and Hospital, JSS Academy of Higher Education and Research, Mysore, Karnataka, India

Correspondence Address:
Dr. Shilpa Padar Shastry
Department of Oral Medicine and Radiology, Vydehi Institute of Dental Sciences, No. 82, EPIP Area, Bengaluru - 560 066, Karnataka
India

Abstract

Background: The clinical feature and radiographic appearance of orthokeratinized odontogenic keratocyst (OKC) are not characteristic, which may lead to the misdiagnosis. The radiographic appearance of OKC may range from a small unilocular radiolucency to a large multilocular radiolucency, resembling other odontogenic cysts and tumors. Aim: The aim was to illustrate the characteristic feature of OKC presented on the digital panoramic radiograph and cone-beam computed tomography (CBCT), which may provide great value for the differential diagnosis and the treatment planning and also to compare the various radiographic features of OKC in CBCT and digital panoramic radiograph. Materials and Methods: Digital panoramic and CBCT records of seven cases, with 11 lesions of OKC were analyzed retrospectively from the patients' database from our institute (2014 to 2016), which was histopathologically diagnosed as OKC. Results: The mean age of the patients was 24.1 years, and the female-to-male ratio was 3: 4. Six of 11 lesions were localized within the mandible, and five lesions were in the maxilla. Conclusion: The presurgical assessment with radiological information is extremely important for treatment planning, and CBCT provides us with an accurate and faster three-dimensional representation of a lesion at a lower dose and cost, but the role of panoramic radiograph cannot be refuted.



How to cite this article:
Shastry SP, Pandeshwar P, Padmashree S, Kumar N N, Garg S, Sanjay C J. Imaging characteristic of 11 lesions of odontogenic keratocyst in the indian subpopulation: A cone-beam computed tomography experience.Contemp Clin Dent 2020;11:20-27


How to cite this URL:
Shastry SP, Pandeshwar P, Padmashree S, Kumar N N, Garg S, Sanjay C J. Imaging characteristic of 11 lesions of odontogenic keratocyst in the indian subpopulation: A cone-beam computed tomography experience. Contemp Clin Dent [serial online] 2020 [cited 2020 Aug 4 ];11:20-27
Available from: http://www.contempclindent.org/text.asp?2020/11/1/20/289507


Full Text



 Introduction



First described by Philipsen in 1956,[1] the odontogenic keratocyst (OKC) arises from the remnants of the dental lamina and basal cells of the oral epithelium.[2],[3] OKC was designated by the World Health Organization (WHO) as a keratocystic odontogenic tumor (KCOT) reclassifying this into developmental odontogenic neoplasia in 2005, reflecting its aggressive clinical behavior, high recurrence rate, association with nevoid basal cell carcinoma syndrome and mutation in the Protein Patched Homolog 1 (PTCH) tumor suppressor gene. Histologically, the two variants, orthokeratinized and parakeratinized were considered as different entities. The parakeratotic variant of OKC was designated as KCOT by the WHO, whereas orthokeratotic variant was excluded from the definition of KCOT and called as orthokeratinized odontogenic cyst (OOC).[3]

In 2017 January, 4th edition of the WHO reverted KCOT from neoplastic category back into the cyst category as OKC, based on extended genetic and molecular data. This is because many studies showed the presence of PCTH gene mutation even in nonneoplastic lesions including dentigerous other cysts. Moreover, the resolution of cyst after marsupialization may occur, while the neoplastic process does not respond. Histologically, OKC is characterized by palisaded and hyperchromatic basal cells with layer with a corrugated surface layer of parakeratin. OOC, which was referred to as a type of OKC originally, later excluded from KCOT in 2005 WHO classification, now accepted as a separate entity for the first time in 2017 WHO classification. OOCs differ from OKCs as the former are not associated with any syndromes, nonaggressive, do not have high recurrence rate, and are predominantly lined by orthokeratinized stratified epithelium.[4]

Imaging plays an important role in the diagnosis of maxillofacial jaw lesions because any cyst or neoplasm can achieve dimensions so substantial that imaging helps to understand the extent of the lesion.[5] Significant number of OKCs have no clinical signs and symptoms until they cause bone displacement, cortical disruption, or pain and are found incidentally during routine radiographic examination. Intraoral periapical, occlusal, and panoramic radiographs provide an initial assessment of the position and size of OKCs.[6] However, cone-beam computed tomography (CBCT) provides high spatial resolution, accurate three-dimensional representation of jaw lesion, borders of large lesions, bone expansion, and cortical perforation with a relatively low dose of radiation.[7] The objectives of this article were to illustrate the characteristic feature of OKCs presented on the digital panoramic radiograph and CBCT, which may provide great value for the differential diagnosis and treatment planning.

 Materials and Methods



Seven cases with 11 lesions were analyzed retrospectively from the patient's database of the Department of Oral Medicine and Radiology, Vydehi Institute of Dental Sciences and Research Center, Bangalore, from 2014 to 2016. The selected cases were histopathologically diagnosed as OKC with both panoramic and CBCT records. Age, gender, history, clinical features including the location of the lesion, associated tooth, cortical plate expansion, and other symptoms were assessed along with consideration for the provisional diagnosis. The digital panoramic radiographs and CBCT were performed with Kodak Carestream CS9300 (Carestream Health, Rochester, NY, USA) with 60 kV, 8.0 mA for panoramic radiographs, and 90 kV at a time of 12–20 s. In orthopantomography (OPG) and CBCT, we assessed for location (maxilla or mandible – anterior, premolar, and molar); size and shape; periphery (well defined or partially diffuse); internal structure (radiolucent – unilocular or multilocular, scalloping); and the influence of the OKC on adjacent structures, such as teeth, buccal and lingual cortices, lower border of the mandible, inferior alveolar canal (IAC), and the maxillary antrum, was noted.

 Results



Clinical features

Seven cases of histopathologically diagnosed as OKC were analyzed. The mean age of the patients was 24.1 years and ranged from 8 to 38 years. The female-to-male ratio was 3:4. There were 11 OKC lesions in seven patients; two patients had multiple OKCs (Case 4 had two OKCs: one in the anterior maxilla and one in the posterior mandible; Case 7 had four OKCs, each in the maxillary and mandibular posterior region). Five of 11 lesions were localized in the maxilla. Six lesions were localized within the mandible [Figure 1]. The recorded duration of the lesion in the form of swelling as recognized by the patients ranged from 1 to 6 months. Six of the 11 lesions presented with pain and swelling, whereas one lesion presented with pain as its sole complaint, while four lesions were asymptomatic without pain or swelling. On clinical examination, four lesions did not show any clinical signs of swelling, tenderness, cortical plate expansion, or perforation; one showed the presence of sinus tract with pus discharge; vestibular obliteration was present in four lesions; buccal or labial cortical plates were expanded in five lesions; lingual or palatal cortical plate was expanded in three lesions; except for one lesion where there was perforation clinically, no other cases showed clinical perforation. Four lesions were provisionally diagnosed as dentigerous cyst, one each as radicular cyst, globulomaxillary cyst, and localized periodontitis [Table 1].{Figure 1}{Table 1}

Radiological findings

Location

Six lesions were localized within the mandible, and five lesions were in the maxilla. All six lesions that were localized in the mandible were located in the posterior retromolar ramus region of the jaws. Of the five lesions occurring in the maxilla, two were located in the anterior region and three in the posterior region. Only one among the 11 lesions occurring in the mandible was observed to cross the midline [Figure 2]. One of the 11 lesions showed incidental findings in the panoramic radiograph [Figure 2] and Case 6]. Apart from a chief complaint, two cases [Case 4 and Case 7] showed the presence of additional lesions in the other quadrants, which were first diagnosed incidentally in panoramic radiographs [Figure 3] and [Table 2].{Figure 2}{Figure 3}{Table 2}

Size

The anterior–posterior dimension of the lesions ranged from 12.3 to 61.3 mm, with latter being the only lesion to be extensive as to even cross the midline [Table 2]. All the lesions were well defined.

Internal structure

In panoramic radiograph, three lesions showed unilocular appearance, two lesions showed multilocular, three lesions with unilocular pericoronal, and two lesions were unilocular envelopmental type of radiolucency. Panoramic radiograph was not conclusive about the internal structure in one of the lesions. In CBCT, six showed unilocular appearance, one with multilocular appearance, and four lesions were unilocular pericoronal radiolucencies with intact follicular spaces [Figure 3] and [Table 2].

Effect on adjacent structure

Three of the 11 lesions were not associated with impacted tooth, and eight lesions were associated with impacted teeth. The impacted teeth were third molars in five lesions; in one lesion second premolar; in one more lesion second molar were involved; in another lesion, two teeth that is lateral incisor and canine was involved. There were no impacted supernumerary teeth in any of the lesions. One out of 11 lesions, panoramic radiograph showed resorption in one, no resorption in nine lesions. In one lesion, panoramic radiograph failed to show the presence or absence of resorption. In CBCT, four lesions clearly showed the presence of resorption, and seven lesions showed no resorption associated with adjacent teeth [Figure 4] and [Table 3]. When we compared the duration of symptoms with the presence or absence of root resorption in CBCT, the maximum duration of symptoms (pain or swelling) reported in patients with root resorption was 4 months; and the patient without root resorption ranged up to 1 year.{Figure 4}{Table 3}

Of the six mandibular lesions, five lesions showed the agreement between OPG and CBCT findings, except one where CBCT showed an intact IAC, and OPG showed the inferior displacement of IAC. Moreover, CBCT could give additional information on the buccal or lingual displacement of IAC and any erosion of the cortical boundaries.

Of the five lesions affecting maxilla, no effects on maxillary sinus or nasal floor in four lesions, and the effect of lesion on maxillary sinus was not clearly defined in one lesion as seen on panoramic radiograph. CBCT clearly showed disruption of one of the walls, perforation, thickening of mucosa in four lesions, and unaffected walls in one lesion [Table 4] and [Figure 5].{Table 4}{Figure 5}

In the panoramic radiograph, thinned out lower cortical borders were appreciated in three lesions, no expansion in four lesions, and expansion could not be commented in the remaining four lesions. In CBCT, nine cases showed expansion, and two did not show any expansion. In addition to these details, perforation and thinning of buccal, lingual, and palatal cortices were clearly visible [Figure 6] and [Table 5].{Figure 6}{Table 5}

Histopathological findings

Histologically, all the cases were characterized by a uniform, usually corrugated parakeratinized epithelium, 8–12 cells thick presenting a flat basal surface lining the fibrous wall. The columnar basal cells showing reversed nuclear polarity is an important feature, and satellite cysts were found in some lesions.

 Discussion



The occurrence of OKC in our institution is 3.6/years. This was more than that of reported in the Hong Kong population, which was 2.1/years.[8] MacDonald-Jankowski expressed that these patients displayed differences between global groups, patients of East Asian origin may present early symptoms, while in the Western community, it may be found as an incidental finding at a later stage of the disease.[9]

Radiologic diagnosis of a lesion depends on the location, internal structure, extension, cortical involvement, periosteal alterations, and relation to the adjacent structures within the jaw. MacDonald-Jankowski and Li evaluated the clinical and conventional radiological features of 33 cases affecting a Hong Kong Chinese community and concluded that those lesions that presented early were significantly associated with unerupted teeth. They also concluded that multilocular lesions had a significant predilection for older patients, longer in mediodistal extension, whereas unilocular lesions had a predilection for the maxilla.[8] The OKCs may begin as unilocular lesions and gradually become multilocular as proposed by Haring and Van Dis in their study.[10] OKCs show minimal buccolingual expansion as compared to ameloblastoma, assuming a fusiform shape rather than the balloon expansion more of the ameloblastoma. Contrary to this, nine lesions showed expansion in CBCT in our cases. One among the 11 lesions showed extensive mandibular involvement crossing midline although lesion was extensive, the patient reported with the swelling of 4-month duration and pain about 2 months only.

In our case series, two cases [Case 4 and Case 7] had multiple OKCs where the additional lesions were detected incidentally, and patients had no signs and symptoms with respect to additional lesions [Figure 3]. Further investigations were done to evaluate for the presence of other systemic abnormalities to rule out of nevoid basal cell carcinoma syndrome and found that both the cases were solitary (or sporadic) or nonsyndromic variety. According to a systematic review, solitary OKC is the most common accounting nearly 94% of all OKCs, and the global recurrence rate of solitary OKC is 28%.[11]

Panoramic and intraoral radiographs are the basic imaging methods in the diagnosis of OKC. In our case series, one case of incidental finding and two cases where multiple OKC were first detected in panoramic radiography, thus establishing the importance of scout radiographs. Although panoramic radiography is the primary choice of radiologic examination for dentists, the superimposition of craniofacial structures generates images with limitations, distortions, and magnifications. Thus, for detailed examinations of the OKC, CBCT can be advised to know the anatomical extensions and dimensions. The risk of injury to adjacent structures such as teeth, mandibular canal, maxillary sinuses, and cortical plates can be evaluated, with reduced radiation dose and cost as compared to multidetector computed tomography (MDCT). The smaller device size and shorter scanning time in CBCT allow it to be a convenient appliance as compared to MDCT. Shweel et al. compared the accuracy of CBCT and MDCT in the preoperative radiological assessment of odontogenic cysts and tumors and found that both CBCT and MDCT were identical in detecting location, borders, and internal structure of examined lesions. They observed that the CBCT was more accurate in linear measurements, identification of tooth displacement, and buccal bone defect and concluded that CBCT is an optimal radiological modality for preoperative radiological assessment of odontogenic tumors.[12]

However, despite all these advantages, CBCT was unable to discern the contents of the lesion. CBCT is insufficient for displaying the contrast within soft tissue, even though, the dynamic range of CBCT has been increased from 8-bit to 14-bit depth. Sometimes, failure to consider the whole image may result in missed neoplasm.[6] Furthermore, a review by MacDonald revealed that CBCT has little to contribute to the imaging of malignancy and its subsequent management. In such patients, MDCT, magnetic resonance imaging (MRI), and positron emission tomography can be used for appropriate imaging.[5]

 Conclusion



OKC, being an aggressive lesion with varied radiographic appearance, may resemble ameloblastoma, dentigerous cyst, lateral periodontal cyst, and radicular cyst. The presurgical assessment with radiological information is extremely important for shaping the surgeon's approach for treatment planning, as incomplete removal may lead to recurrence. CBCT provides us with an accurate and faster 3-dimensional representation of a lesion at a lower dose and cost. Nevertheless, the role of 2-dimensional radiographs like panoramic radiograph as well as other advanced imaging such as MRI and MDCT cannot be refuted.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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