Introduction
Ever since Philipsen described the odontogenic keratocyst (OKC) in 1956, the lesion has turned into a center of momentous clinical interest because of its unusual growth pattern and tendency to recur even after surgical removal (Sulabha et al., 2013). This lesion was recently renamed by Philipsen as keratocystic odontogenic tumour (KCOT) and reclassified as an odontogenic neoplasm in the World Health Organization’s, 2005 edition of its histological classification of odontogenic tumours. According to this edition, the KCOT has been defined as a benign uni or multicystic intraosseous tumour of odontogenic origin, with a characteristic lining of parakeratinized stratified squamous epithelium and potentially aggressive, infiltrative behavior (Çakur et al., 2008; MacDonald- Jankowski, 2011). Odontogenic Keratocyst (OKCs) of the jaw is also recognized as a developmental cyst and there is general agreement that the odontogenic keratocyst arises from the cell rests of the dental lamina. This cyst shows a different growth mechanism and biologic behaviour unlike the other more common jaw cysts and tumors (Neville et al., 2002; Avinash et al., 2010). Odontogenic keratocysts may be found in a wide range of patients who range in age from infancy to old age. KCOTs are twice more frequent in the mandible than in the maxilla (Scartezini et al., 2012) and mandible is occupied in 60% to 80% of cases.. Radiographically, OKCs appear as well-defined radiolucencies, which can be either unilocular or multilocular and they may appear as small or large, round or ovoid radiolucent lesions, often with scalloped, multilocular, distinct sclerotic margins. This type of cyst may occur in conjunction with an impacted tooth as has been reported in 25 to 40% of cases; in such instances, the radiographic features suggesting more towards a diagnosis of dentigerous cyst while smaller cysts makes the diagnosis more dilemmatic (Neville et al., 2002; Hiremath et al., 2011; Scartezini et al., 2012; ).

Case Report
A 23 year old male patient reported the Department of Oral Medicine and Radiology with a chief complaint of swelling in lower front tooth region and face since last 1 year when he suddenly noticed a small swelling in the lower right front tooth region inside the mouth and he took some medication. After taking those medications, the swelling completely subsided. After 6 months, similar swelling appeared which was progressively increasing in size and was not subsided by taking medication. The swelling continued increasing in size and affected the other teeth on opposite side also. After 10 days, he noticed swelling on face in mirror. He immediately went to local dentist who advised for a biopsy. Clinical examination revealed a single, ill defined swelling present in relation to the lower 1/3 rd of the face near symphysis and parasymphysis regions which crossed midline and was measuring approximately 5X3 cm in diameter extends mesiodistally from right parasymphyseal region to left parasymphyseal region and superioin- feriorly from the vermilion border of lip of right side and corner of mouth of left side till 1 cm below the lower border of mandible. Swelling appeared to be with smooth surface with shiny, slightly stretched skin and on palpation, swelling appeared to be bony hard in consistency with well-defined margins and with a smooth lobular surface (Figure1). Swelling was slightly tender on right side with no local rise in temperature. Superficial skin was pinchable with no secondary changes (Figure 2). Intra-orally, mandibular vestibule was obliterated by swelling in relation to 35 to 43 region. On detailed intraoral examination, a single well defined swelling was present in anterior part of mandible extending from 35 to 43 region with buccolingual expansion. Buccally, swelling extended mesiodistally from mesial aspect of 43 to the distal aspect of 35 crossing midline and buccolingually from the alveolar crest to the buccal and labial vestibule obliterating the vestibular region. Superficial alveolar mucosa appeared to be stretched with detachment of the marginal gingiva in relation to 33, 34, 35. Swelling was slightly tender on right side. Swelling was bony hard in consistency with egg shell crackling which was present distal to 33. Bucco-lingual expansion was seen evident throughout the swelling (Figure 3, 4). On pulp vitality test, 32 was found to be completely non-responding while 35 showed delayed response.

During aspiration, a dark blackish-red betadine coloured aspirate was taken out (Figure 5). IAOPAR irt 31, 32,33,41,42,43 were advised. IOPAR revealed multilocular well defined radiolucencies overlapping each other at the apical regionof 31,32,33,41,42. Margin of the radiolucencies were sclerotic (Figure 6, 7). Orthopantomogram showed well defined multilocular radiolucency extending from the periapical region of 35 till the peripical region of 43,44. Sclerotic margin with displacement of teeth could be appreciated. The lower border of the radiolucency overlapped and crossed the inferior border of mandible. Apical 1/3 of roots in relation to 33,35,43,45 appeared knife edged suggestive of root resorption (Figure 8). Mandibular topographic occlusal radiograph was performed to check the buccolingual expansion. In this radiograph, multilocular radiolucency was evidently seen in the apex of 33,32,32,41,42 region. A thin sclerotic line was also appreciated on the buccal aspect of 32, 33,34,35 suggestive of buccolingual expansion. Inferior border of mandible appeared intact (Figure 9). On the basis of clinical examination and chair side investigations, a provisional diagnosis was made for central giant cell granuloma with differential diagnosis of Glandular odontogenic cyst, Aneurysmal bone cyst, Ameloblastoma, Odontogenic keratocyst, and an Arteriovenous malformation in relation to 35 to 43 region. The lesion was examined at biopsy. Histopa- thologically, H & E staining showed epithelia overlying the connective tissue stroma. The epithelium was parakeratinized, stratified squamous, 8-10 layer thick. Basal cells were tall columnar in appearance with hyperchromatic nuclei, exhibiting reverse polarity. Loss of cellular adhesion and subepithelial split could also be seen. Connective tissue stroma showed juxtaepithelial hyalinization and was sparsely cellular with loose collagen fibres, acute inflammatory cell infiltrate and areas of haemorrhage (Figure 10). Surgical enucleation was performed under all aseptic precautions and was started antibiotic prophylaxis. Complete enucleation with aggressive curretage was performed. Patient was kept under repeated follow-up for three months. Patient was re-called after 3 months and after 9 months (Figure 11).

Discussion
An insight into the times past of odontogenic cysts goes back to the 19th century, when the odontogenic keratocyst (OKC) was first described in the year 1876 and was named by Phillipsen in 1956 (Neville et al., 2002) who described it as a different entity characterized by a keratinized lining, presence of satellite cysts and association with the nevoid basal cell carcinoma syndrome (Nagraja et al., 2012). Philipsen and Riechert.

have suggested that OKC should be considered as a benign tumour and hence be called as KCOT or keratocystic odontogenic tumour. Shear has countered this argument by saying that even if it is a neoplasm, it is suitable to be called as OKC as many neoplasms do not essentially have a suffix ‘oma’. This debate was started by Shear (2003) that OKC should be called as keratocystoma which led Philipsen and Riechert suggesting keratinising cystic odontogenic tumour in 2004 and then Philipsen suggesting keratocystic odontogenic tumor again in 2005 (Jyothi et al., 2010). This cyst has a propensity for recurrence and the aggressive behaviour clinically and histologically has necessitated the reclassification of the lesion by the World Health Organization (WHO, 2005) as a ‘keratocystic odontogenic tumor’ (KCOT). The KCOT is defined as ‘a benign uni- or multicystic, intra-osseous tumor of odontogenic origin, with a characteristic lining of parakeratinized stratified squamous epithelium and potential for aggressive, infiltrative behaviour (Çakur et al., 2008; MacDonald- Jankowski, 2011; Rajkumar et al., 2011). Odontogenic Keratocyst (OKCs) of the jaw is a type of developmental cyst and there is general agreement that the odontogenic keratocyst arises from cell rests of the dental lamina. This cyst shows a different growth mechanism and biologic behaviour from the more common dentigerous cyst and radicular cyst (Neville et al., 2002; Avinash et al., 2010). Around 60% of all cases are diagnosed odontogenic keratocysts in people typically being found in adults in the second to fourth decades of life and with a slight male predilection (M:F=1.6:1). The age distribution appears to be bimodal. There appears to be two peaks of incidences between 25-34 years and 55-65 years of age.The mandible is occupied in 60% to 80% of cases, with a marked tendency to involve the posterior body and ascending ramus where anterior mandible is an uncommon site with the lesion crossing the midline (Neville et al., 2002; Sulabha et al., 2013). In maxillary region, there are inconsistencies regarding the predominant location of OKCs. One study shows that OKCs are distributed evenly between the anterior and posterior regions of maxilla; some show that there are more anterior lesions than posterior lesions and others concluded that the posterior region is more predominant site (Hiremath et al., 2011). Patients with keratocysts may complain of pain, mobility of teeth in the affected area, swelling, or discharge. Nasal obstruction, paresthesia, and root erosion are more rare symptoms. Occasionally diseased person may experience paresthesia of the lower lip or teeth. In many instances, patients were amazingly free of symptoms until the cysts reached a large size and involved the maxillary sinus and the entire ascending ramus, including the condylar and coronoid processes. These patients may be unacquainted of the lesions until they build up pathologic fractures or may be incidental finding during examination (Çakur et al., 2008; Avinash et al., 2010). In our case, the patient did not spontaneously complain of pain, and was initially referred for opinion and biopsy as swelling didn’t subside for long. This type of cyst tends to expand in an antero-posterior direction within the medullary cavity of the bone without causing obvious bone expansion and this unique feature often becomes useful in its clinical and radiographic diagnosis because dentigerous and radicular cysts of comparable size are usually associated with bony expansion (Neville et al., 2002; Hiremath et al., 2011) which was not similar to our clinical finding in this case. Radiographically, OKCs appear as well-defined radiolucencies, which can be either unilocular or multilocular. They typically extend into the marrow cavity with either a smooth border contributing to mild bulging of the cortex but without significant cortical expansion. Keratocystic odontogenic tumors can show a more aggressive growth pattern including multilocularity, cortical expansion, perforation of the cortical bone, tooth and mandibular canal displacement, root resorption, and extrusion of erupted teeth (Devenney-Cakir et al., 2011). Unilocular OKCs can be located periapically, simulating periapical cysts; between the roots of teeth, simulating lateral periodontal cysts or lateral radicular cysts; surrounding the crown of unerupted teeth, simulating dentigerous cysts; or in the maxillary midline, simulating nasopalatine duct cysts. Large unilocular OKCs can be impossible to tell apart from cystic ameloblastomas. OKCs have a tendency for intra-osseous growth, more often in a longitudinal than in a transverse direction (minimal expansion), as seen in this case, thereby replacing the bone marrow, rather than giving rise to periosteal bone formation, which would result in a bony swelling. Rapid growth does not allow enough time for the periosteum to lay down new bone. These different types of appearances of OKC make diagnosis more dilemmatic as in our present case. The luminal content can have different consistencies described as a “straw-colored fluid”, “thick pus-like” material or a caseous, thick, cheesy, milk white mass (Rajkumar et al., 2011). But in our case aspiration finding was exclusively different which were more suggestive of an aspirate from arterio-venous malformations or Aneurysmal Bone Cyst. Histologically, KCOTs have been classified by some authors into parakeratotic and orthokeratotic subtypes. Classification is based on the lining and the type of keratin produced. Compared with the parakeratotic subtype, the orthokeratotic subtype produces keratin more closely resembling the normal keratin produced by the skin, with a keratohyaline granular layer immediately adjacent to the layers of keratin, which do not contain nuclei. The parakeratotic subtype has more disordered production of keratin; no keratohyaline granules are present, and cells slough into the keratin layer. However, in case of OKCs the lining epithelium is highly characteristic and consists of keratinized surface (parakeratinized- 83% and orthokeratinized-10%) which is typically corrugated. Thickness of the epithelium is found uniformly arranged with 6 to 10 layers without rete-ridges (Çakur et al., 2008).The keratin contains nuclei and is referred to as parakeratin. The parakeratotic type is the most frequent (80%) and has a more aggressive clinical presentation than the orthokeratotic variant. Histopathological picture shows presence of a well defined, often palisaded, basal layer consisting of columnar or cuboidal cells; intensely basophilic nuclei of columnar basal cells oriented away from the basement membrane; parakeratotic layers, often with a corrugated surface; and mitotic figures frequently present in suprabasal layers (Çakur et al., 2008; Scartezini et al., 2012). This palisade like arrangement of basal layer is often described as “picket fence” or “tombstone” appearance. Upper portion of the epithelium is composed of stratified squamous epithelium with high mitotic index without any clear cell formation. Epithelial plaque formation is absent in OKCs but the connective tissue wall often shows small islands of epithelium (Hiremath et al., 2011). OKCs have a high recurrence rate ranging from 2.5 to 62 % (Sulabha et al., 2013; Hiremath et al., 2011) and after they occur due to incomplete removal of the original cyst’s lining, thin friable cystic lining, growth of the new OKC from small satellite cyst of odontogenic epithelial cell rests left behind after surgical treatment, or by development of an unrelated OKC in an adjacent region of jaw which is interpreted as a recurrence (Rajkumar et al., 2011; Sulabha et al., 2013). The recurrence of OKC is thought to be based on great mitotic activity and growth potential found in epithelium, further than other sources of recurrences such as remnants of dental lamina and epithelial islands (Silvaa et al., 2006). There is no doubt that recurrences may arise if any part of the lining is left behind. All efforts should, therefore, be made at proper enucleation and elimination of possible remnants of the cyst wall in case the cyst ruptures and has to be removed piecemeal. There is also a possibility.

that microcysts are present in the connective tissue of the cyst wall and that these are left behind after enucleation. Some keratocysts show active budding of the basal layer of the epithelial lining that may reach to the periphery of the connective tissue wall and, therefore, may also be the source of a true recurrent cyst. The third reason for a recurrent OKC is the development of a new keratocyst from an epithelial island or microcyst left behind in the mucosa (Stoelinga, 2005). A recent study suggests that PTCH1 mutations, particularly those causing protein truncations, are associated with OKCs showing increased proliferative activity and thus related to a phenotype of higher recurrent tendency. When taking into consideration removal of a keratocyst, however, it is important to keep in mind the 3 possible reasons why an OKC could recur as stated above. Therefore, treatment should aim at complete elimination of possible vital cells left behind in the defect. In Browne’s series, three different treatment methods were evaluated, which were marsupialization, enucleation and primary closure, and enucleation and open dressing (Rajkumar et al., 2011). There was no correlation between treatment method and the rate of recurrence. Morgan and colleagues categorize surgical treatment methods for KCOT as conservative or aggressive. Conservative treatment of OKC is “cyst-oriented” and, thus, includes enucleation, with or without curettage, or marsupialization. Aggressive treatment addresses the “neoplastic nature” of the KCOT and includes peripheral ostectomy, chemical curettage with Carnoy’s solution or en bloc resection (Avinash et al., 2010; Rajkumar et al., 2011). Enucleation has a benefit over marsupialization as complete specimen can be sent for histopathologic examination (Rajkumar et al., 2011). The purpose of using Carnoy’s solution is to provide a total elimination of epithelial remnants from the cyst walls, which may cause recurrences (Scartezini et al., 2012). Researchers have suggested that the recurrence rate is relatively low with aggressive treatment, whereas more conservative methods tend to result in more recurrences and after the combined therapy of enucleation and Carnoy’s solution, the recurrence rate was found to be 9% (Ozkan et al., 2012). Recurrence is documented in many cases even after 10 years of follow up and treatment.

Conclusion
In conclusion, benign uni- or multicystic intraosseous tumors of odontogenic origin should be considered in the differential diagnosis of jaw lesions. Due to variation of its clinical and radiological appearances diagnosis, becomes confusing and tricky. In spite of, even in the incidence of clinical and radiological features suggestive of KCOT, a definitive diagnosis cannot be made without microscopic investigation. Only thorough investigation will allow to arrive at the most effective treatment and thus to pass up the recurrences.

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