|Year : 2014 | Volume
| Issue : 4 | Page : 287-289
Orthokeratinized odontogenic cyst
Ramakrishnan Bharathi, Gnanadeepam Santiago, Parthiban Nallaiyan
Department of Oral Pathology and Microbiology, Tamil Nadu Government Dental College and Hospital, Chennai, Tamil Nadu, India
|Date of Web Publication||20-Nov-2014|
Department of Oral Pathology and Microbiology, Tamil Nadu Government Dental College and Hospital, Chennai - 600 003, Tamil Nadu
Odontogenic keratocyst is a cyst derived from the remnants of the dental lamina, with a biologic behavior similar to benign neoplasm and it is now designated as keratocystic odontogenic tumor (KCOT) in the new World Health Organization classification. Orthokeratinized odontogenic cyst (OOC) is a rare developmental odontogenic cyst that has been considered as a variant of KCOT until Wright (1981) defined it as a different entity. The OOC is a specific odontogenic clinicopathological entity that should be differentiated from the KCOT as it presents a completely different biological behavior. Here we present a case of OOC in a 19year-old male patient and review on its clinical and histological aspects.
Keywords: Granular cell layer, keratocystic odontogenic tumor, orthokeratinization
|How to cite this article:|
Bharathi R, Santiago G, Nallaiyan P. Orthokeratinized odontogenic cyst. SRM J Res Dent Sci 2014;5:287-9
| Introduction|| |
The orthokeratinized odontogenic cyst (OOC) is a relatively rare developmental odontogenic cyst arising from the cells rests of the dental lamina.  OOC was initially defined by World Health Organization (WHO 1992) as an uncommon orthokeratinied type of odontogenic keratocyst (OKC). 
Orthokeratinized odontogenic cyst was first described as a dermoid cyst by Schultz in 1927. Philipsen (1946) considered it to be a type of OKC.  Wright in 1981 specified its clinicopathological aspects and suggested that it to be called as OKC-orthokeratinized variant. 
The term OOC is the most accepted terminology as coined by Li et al in 1998. .  OOC represents 7-17% of all keratinizing jaw cysts.  The WHO (2005) new classification for head and neck tumors has designated OKC as keratocystic odontogenic tumor (KCOT) and reclassified it as a neoplasm in view of its intrinsic growth potential and propensity to recur. 
| Case report|| |
A 19-year-old male reported to our institution with a chief complaint of swelling in the lower jaw for the past 3 months. His past medical history was not relevant, and general physical status was good.
On extra oral examination, diffuse swelling was present in the right parasymphysis region of 2 cm × 2 cm in size, hard in consistency and nontender [Figure 1].
On intra oral examination, swelling was seen in relation to retained deciduous 83, 44 and 45 region, obliterating the buccal vestibule, hard in consistency, nontender with bicortical expansion and lingually tilted 44 and 45 [Figure 2].
|Figure 2: Intra oral examination reveals obliterated buccal sulcus, with retained 83|
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Orthopantomograph revealed a unilocular radiolucency extending from 33 to 46 region, with impacted 43 and root resorption was seen in 31, 32, and 42 [Figure 3].
Provisional diagnosis of OKC was given. Incisional biopsy was done and sent for histopathological examination. On microscopic examination, it showed a cystic lesion with an orthokeratinized stratified squamous epithelial lining and a fibrous connective tissue wall. The epithelium was of 4-6 layer thickness with surface corrugation and prominent granular layer. The basal cells were low cuboidal. Histopathology was that of OOC.
Following which, enucleation was done under general anesthesia, and the specimen submitted for histopathological examination.
Gross examination of the excised specimen revealed a cystic lining, keratin material and extracted teeth from 31 to 46 including 83 [Figure 4].
|Figure 4: Grossing specimen showed cystic bag along with extracted teeth|
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Histopathology was consistent with the preoperative diagnosis of OOC [Figure 5] and [Figure 6].
|Figure 5: Orthokeratinized stratified squamous epilthelial lining with fibrous connective tissue wall (H and E, ×4)|
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|Figure 6: Orthokeratinized stratified squamous epilthelial lining with a prominent granular cell layer (H and E, ×10)|
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| Discussion|| |
Orthokeratinized odontogenic cyst occurs predominantly in young adults and show 2:1 male:female ratio.  The mandible was more commonly involved than the maxilla, the most common location being the mandibular molar and the ramus region.  The size can vary from <1 cm to >7 cm in diameter.  OOC almost appears clinically and radiographically representing dentigerous cyst as they most often involved an unerupted mandibular third molar. 
Swelling is the most frequent symptom and is accompanied with pain although in most of the cases, the lesion is asymptomatic.  Large lesions can cause cortical expansion. 
Radiographically the cyst appears as a well-circumscribed, unilocular, or multilocular radiolucency that occasionally is associated with an unerupted tooth or with the root, without causing resorption.  Both the OOC and KCOT show similar findings clinically regarding age, sex and site of occurrence but the OOC are generally solitary asymptomatic lesions whereas KCOT associated with nevoid basal cell carcinoma syndrome exhibits multiple lesions. 
Histologically, OOC have a thin lining with a flat orthokeratinized stratified squamous epithelium, a prominent granular cell layer and a flat epithelium connective tissue interface.  Basal cells are flat or low cubiodal and not palisaded compared with keratocystic odontogenic tumor which has a parakeratinized squamous lined cyst with a palisaded basal layer and a corrugated surface.  Epithelium often sloughs off from the connective tissue (94% of the time). 
Satellite or daughter cyst which is common in keratocystic odontogenic tumor is not seen in OOC.  Keratocystic odontogenic tumor is also called as parakeratinized OKC. 
Orthokeratinized odontogenic cyst was more often associated with an impacted tooth (75.7%), when compared with 47.8% for the parakeratinized OKC.  Recurrence rate in parakeratinized OKC is seen in 42.6% of the cases, compared with only 2.2% for OOC. 
Due to the less aggressive clinical behavior and recurrence pattern of the orthokeratinized variant, the designation of the orthokeratinized variant warranted a separate entity, "OOC." 
Recent immunohistochemical studies that compared the OOCs with KCOTs have shown distinct differences in the expression of Ki-67 proliferative index, p53, p63 and bcl-2.  Reduced expression of all these markers in OOC reflect that they have a different cell differentiation and exhibit a lower cellular activity than the keratocystic odontogenic tumor. 
The OOC does not show the activity of epithelial membrane antigen and carcinoembrionary antigen whereas the keratocystic odontogenic tumor shows this activity.  The reactivity to cytokeratins has showed differences as OOC stains to cytokeratins 1, 2, and 10 which would suggest a normal differentiation of the epidermis whilst the keratocystic odontogenic tumor reacts to cytokeratins 4, 13, 17, and 19, demonstrating that these are different entities. 
Surgical enucleation with curettage is the treatment of choice for the OOC.  Peripheral ostectomy of bony cavity and chemical cauterization with Carnoy's solution is advocated for keratocystic odontogenic tumor due to high recurrence rate. 
| Conclusion|| |
Orthokeratinized odontogenic cyst presents a completely different biologic behavior compared with KCOT. Hence, it is necessary to possess a thorough knowledge of clinicopathological differences between the most aggressive keratocystic odontogenic tumor and the less aggressive OOC, so that patient receives the most appropriate treatment.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]