Keratocystic Odontogenic Tumor (KCOT): a report of three cases

Keratocystic odontogenic tumor (KCOT), formerly known as odontogenic keratocyst (OKC) is a benign unicystic or multicystic intraosseous neoplasm of odontogenic origin affecting the jaws which manifests itself as a radiolucent unilocular or multilocular lesion. KCOT has unique & characteristic features including potentially aggressive behaviour, high recurrence rate and its association with basal cell nevi bifid rib syndrome. The most common clinical presentation is swelling and affects mandible frequently than maxilla. We report three cases of keratocystic odontogenic tumor of mandible, diagnosed on the basis of distinct radiological and histopathological findings.

Key Words: Keratocystic Odontogenic Tumor; Radiolucent, High rate of recurrence.

Received : 11 Oct 2012 Accepted : 15 Dec 2012 Published: 10 Dec 2012

INTRODUCTION

he diagnostic metamorphosis of odontogenic Tkeratocyst into a recognized cystic neoplasm, keratocystic odontogenic tumor (KCOT), occurred after observation of its biologic behaviour and modern investigations revealed chromosomal and genetic abnormalities with neoplastic

[1] progression .Although it is generally agreed that some features of KCOTs are those of a neoplasia, notably the relatively high proliferative rate of epithelial cells, controversies over the behavior and management of this entity still exist. This lesion was first described in 1956 by Phillipsen as 'Odontogenic Keratocyst' while Pindborg and Hansen in 1963, described the essential features of this type of cyst. It is one of the most aggressive odontogenic cysts of the oral cavity. KCOT is known for its rapid growth and its tendency to invade the adjacent tissues including bone. It has a high recurrence rate and is associated

[2].with the basal cell nevus syndrome This article is intended to review this intriguing entity and to highlight the importance of proper diagnosis of keratocystic odontogenic tumor in three patients with appropriate treatment and follow up.

CASE SERIES

CASE 1

A 65 year-old female patient reported to the Department of Oral Medicine and Radiology, with a complaint of swelling, pain and displaced teeth in the right lower front teeth region since past 3 months. Extra oral examination revealed presence of solitary, diffuse swelling of size 1.5cm x 1.0cm, present in the right side of the face below the lower lip region. Intraoral examination revealed mild obliteration of the labial vestibule w.r.t. 43 42, 41 region. Pathologic migration was evident in 43 & 42 region. Intraoral radiographs (IOPA & Occulusal) revealed unilocular cystic radiolucency extending from coronal third of 43

to apical third of 41 region, flaring of roots w.r.t. 43 & 42 region, cortical plate thinning without its significant expansion (Figure 1). No evidence of external root resorption was noted.

OPG revealed presence of interradicular radiolucency measuring around 1.5cm x 1cm involving the roots of 43 & 42 and extending till the periapex of 41 region. Lesion was corticated inferiorly, whereas superiorly extended till the middle third of roots of 43and 42 (Figure 2). Surgical enucleation of the cyst, with curettage of the defect and administration of Carnoy's solution was carried out under General Anesthesia in Dept. of Oral Surgery. Cystic lining measuring around 1 x 2cm was obtained and was sent for histopathological examination that revealed corrugated parakeratinized stratified squamous epithelium about 8-10 cell layer thick. The basal cell layer was tall columnar and showed prominent palisaded appearance. The underlying connective tissue was fibrous connective tissue, with few capillaries. Histopathological diagnosis was suggestive of KCOT.

Follow up of the patient was done. One year follow up OPG revealed no recurrence. (Figure 3)

1 1 1 1 2Vibha Jain , Siddharth Gupta , Upasana Sethi Ahuja , Shilpa Dua , Poonam

1Department of Oral Medicine & Radiology,I.T.S. Dental College, Hospital & Research Centre ,Greater Noida, Uttar-Pradesh,India.2Department of Orthodontics,E.S.I.C. Dental College & Hospital, New Delhi..

Abstract

Address for correspondence*Dr. Siddharth GuptaReader, Dept. Oral Medicine & RadiologyI.T.S. Dental College, Hospital & Research Centre,Greater Noida (U.P.)E mail : drsiddharthgupta13@gmail.com

Asian Journal of Medical and Clinical Sciences Case Report

Figure 1: Case 1 IOPA revealing unilocular cystic radiolucency extending from coronal third of 43 to apical third of 41 region, flaring of roots.

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Figure 3: Case 1 Post operative 1 year follow up without recurrence.

CASE 2

A 24 year-old male patient reported to Department of Oral Medicine & Radiology with chief complaint of pain & swelling in the lower left front teeth region since 4 1/2 months. No history of trauma reported was in that region. Intra-oral examination revealed presence of diffuse swelling in the lower left anterior vestibular region extending from mesial of 42 to distal of 34 region, with evident pathologic migration of 33. Extra oral examination exhibited no facial asymmetry. Intraoral radiographs revealed areas of multilocular radiolucency w.r.t anterior mandibular region causing lingual cortical plate expansion with overall thinning. Breach in the continuity of lamina-dura of the involved teeth, loss of periodontal ligament space, no evidence of any external root resorption but pathologic migration of root of 33 on the distal aspect was seen.(Figure 4)

Panoramic radiograph revealed presence of a well-defined radiolucency surrounded by a well-corticated radiopaque border with scalloped outline (contributing to multilocular appearance) extending from mesial of 43 to distal of 37, crossing the midline.

CBCT revealed large expansile, osteolytic lesion in the mandible crossing the midline extending from the right parasymphyseal region (mesial of 44) across the midline symphysis till the right body of mandible (in relation to 36), measuring approximately 1.4 x 5.5 x 2.7 cm in antero-posterior, transverse & supero-inferior dimensions. Margins of the lesion are well-defined & corticated. There is expansion, thinning of the mandibular labio-buccal & lingual cortices with focal effacement in the symphysis, right parasymphysis & body regions. There is displacement of roots of 32 & 33 with no evidence of root resorption.(Figure 5)

Surgical marsupialisation of the lesion and administration of Carnoy's solution was carried out under general anesthesia in Dept. of Oral Surgery. Patient was kept on follow-up and no recurrence was seen on post-operative radiograph. (Figure 6)H&E section showed parakeratinised stratified squamous epithelium about 6-7 cell thickness, surface corrugation was seen in some areas and the basal layer revealed palisading and hyperchromatism. The underlying connective tissue capsule showed dense fibrous with plenty of chronic inflammatory cells, and capillaries filled with RBCs suggestive of KCOT.

Figure 2: Case 1: Panoramic radiograph revealing unilocular, interradicular radiolucency involving the roots of 43 & 42 and extending till the periapex of 41 region

Figure 4: Case 2 Occlusal radiograph revealing multilocular radiolucency w.r.t anterior mandibular region causing lingual cortical plate expansion with overall thinning.

Figure 5: Case 2 CBCT Image revealing large expansile, osteolytic lesion in the mandible crossing the midline

Figure 6: Case 2 post operative follow-up

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CASE 3

A 48-year old male patient reported to Department of Oral Medicine & Radiology with complaint of difficulty in chewing from upper and lower left back tooth region since 7 to 8 months. Intraoral examination revealed missing 26, 35 & 46. Intraoral examination revealed Grade I mobility w.r.t 36 37 38. Treatment plan was formulated and to support the same. Intraoral radiographs were taken. IOPA of 35 & 36 region revealed the radiolucency in the periapex of 36, the posterior extent of which could not be traced.

Further, OPG revealed well-defined, scalloped, unilocular (exhibiting multilocularity in few place), radiolucency extending from distal root of 36 involving the entire ramus to sub-condylar region. No breach in the continuity in the posterior margin of left ascending ramus was evident. There was thinning of the cortical plate on the involved side along with displacement of the inferior alveolar nerve canal inferiorly. (Figure 7)

CBCT revealed a large non-expansile osteolytic radiolucent lesion with distinct scalloped margins was evident in the left hemi-mandible including the body, ramus & sub-condylar region. Mild expansion of the lingual cortex of left mandibular ramus was seen without obvious evidence of extra-osseous infiltration. Cortical thinning and inferior displacement of the left inferior alveolar canal was also seen. Imaging findings were suggestive of an odontogenic cyst or neoplastic process (Figure 8).

Surgical marsupialisation of the lesion and administration of Carnoy's solution was carried out under general anethesia in Dept. of Oral Surgery. Patient was kept on follow-up programme.

H&E section showed corrugated parakeratinised stratified squamous epithelium about 6-8 cell thickness, tall, columnar basal cell layer and showing palisading. The underlying connective tissue capsule is fibrous with plenty of chronic inflammatory cells, and capillaries filled with RBC's suggestive of KCOT.

Figure 7: Case 3 OPG revealing well-defined, scalloped, unilocular radiolucency extending from distal root of 36 involving the entire ramus to sub-condylar region.

Figure 8: Case 3 CBCT Image revealing non-expansile, osteolytic radiolucent lesion with distinct scalloped margins involving left hemi-mandible including the body, ramus & sub-condylar region.

DISCUSSION

KCOT is a benign intraosseous neoplasm, with characteristic histopathological features, exhibits potentially aggressive behaviour and has high recurrence rate. KCOT's

[3] comprise approximately 11% of all cysts of the jaws . Since its' inception several studies conducted have shown variations in the patient demographics, clinical behaviour and radiographic features in KCOT globally.

S.NO Criteria for Recurrence

1 Abtropfung is present histologically

2 Daughter cysts are seen histologically

3 The epithelium is separated from the connective tissue histologically

4 Cysts are component of NBCCS

5 Radiologically the cyst is large & multilocular

6 Enuleation tends to be difficult

Table 1: Criteria for Recurrence

Male predominance was reported in KCOT, the general distribution being 60% male and 40% females in studies

[4-9]conducted by Chow H.T et al, Crowley TE et al, Habibi et al. In contrast to male predominance, studies by Chirapathmsakul et al in Thailand and Maurette et al in Brazilian population have shown

[3, 10]female preponderance. P.G. Alva et al reported that both [11, 12]genders have been affected evenly . In our reported cases, two

patients were male and one was a female.

The age range reported by Dolphine Oda e al (2000) in KCOT was 7 - 93 years. In majority of the studies conducted so far a peak incidence in third decade of life followed by the second

[4, 7, 11, 13]decade has been reported However, a major peak of frequency was reported in the fifth and sixth decades of life in Greek population by Kakarantza et al. A bimodal distribution has

[9, 14]also been found in other series . Out of our three cases, one case was in second decade; while the other two were in fifth and sixth decades of life. The mean age of patients with multiple KCOTs, with or without NBCCS, was lower than in those with single

13,15,16,17KCOTs – a result similar to those reported previously .

The mandible is involved more frequently than the maxilla: the percentage of KCOTs occurring in the mandible

[4-6,8,13,18] ranges from 65-83% The mandibular molar and post-molar [6, 8]regions are the more common site of occurrence than the

[7, 10, 12,18,19,20]maxillary posterior region. . All our reported cases were found in the mandible. In contrast to the preferred site predilection, two of them were present in the anterior region and

one in the post-molar region.

Myoung et al 2001 in a review of 256 patients reported the incidence of signs and symptoms most frequently found - swelling at first admission (46.1%), pain (19.9%), swelling and pain simultaneously (16.4%), purulent discharge (6.6%),

[6]discomfort (4.7%) and paraesthesia (0.8%). Some of the other signs and symptoms reported were cellulitis, abscess and trismus [5,10].Patients with no symptoms and lesions found incidentally on

[6, 10, 21]radiographs (5.5% -42.5%) . Two of our patients came with chief complaint of pain and swelling while the third one was an incidental finding on OPG along with trismus as the chief complaint.

Radiographically, KCOTs appears as a unilocular or multilocular lesion with a scalloped contour and corticated

[2]margin KCOTs tend to grow in an anteroposterior direction within the medullary cavity of the bone without causing obvious bone expansion. None of our cases exhibited bone expansion. Stoelinga et al presented the typical radiographic features of keratocyst in 51.21% of cases – of which unilocular appearance was seen in 48.78%, scalloping features in 20.73%, multilocular presentation in 21.95% & ascending ramus involvement was

12 seen in 38.88% in his study. Nakamura and Tsukamoto also [23, 24] reported similar findings. Two out of our three cases,

exhibited scalloped borders giving it a multilocular appearance of which one of the lesions involved ascending ramus. The third case was seen in the anterior mandible and was of unilocular variety.

Brannon RB (1976) stated that displacement of impacted or erupted teeth; root resorption, root displacement or extrusion

[25]of erupted teeth may be evident. Two of our cases showed radiographic root displacement with none of the cases exhibiting root resorption.

Advanced imaging modalities like computed tomography, magnetic resonance imaging, cone beam computed tomography aid in formulating a correct diagnosis of KCOT because of its radiographic resemblance to lesions like ameloblastoma.

Histopathologically, KCOT typically show a thin, friable wall, which is often difficult to enucleate from the bone in one piece, and have small satellite cysts within fibrous wall. Brondum and Jenson in 1991, correlated rate of recurrence with histopathological findings using the Forssell histopathological

[26]classification of KCOT. Several criteria have been proposed in [22]predicting the recurrence of KCOT (Table 1) .

Majority of recurrences appear within the first five years after treatment though recurrence has been reported after 9 years

[7] or more years of initial treatment also. Of the three patients, we have the follow up of more than two years for two cases, with no evidence of recurrence till date.

The treatment depends on several factors that include age of the patient, location, size of the lesion and whether the lesion is primary or recurrent. The goals of the treatment include eradication of pathologic lesion, reduction of the potential for recurrence, preservation of the continuity of jaw and maintaining jaw function and stability. Various treatment modalities include total enucleation with or without peripheral osteoctomy, treatment for lowering the recurrence by removing the

[6]epithelium (Myoung et al ) , excision of overlying mucosa, attached mucosa & treatment of bony defect with Carnoy's

[12]solution.(Stoelinga ) .

CONCLUSION

A thorough knowledge of the clinical, radiological and histopathological manifestations of KCOT on the part of the dental surgeon is important for early diagnosis of the lesion so that optimal treatment can be rendered.

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