Immunohistochemical Evaluation of Proliferating Cell Nuclear Antigen in Odontogenic Keratocyst, Dentigerous Cyst, Radicular Cyst and Ameloblastoma

INTRODUCTION: Odontogenic tumors are lesions derived from epithelium and mesenchymal elements of tooth forming apparatus and therefore exclusively found in jaw bones. Odontogenic tumors compromises a heterogenous group of lesions that ranges from hamartomatous to benign and malignant neoplasms of variying aggressiveness. Odontogenic tumors are very infrequent lesions compared to other pathological process of oral and maxillofacial regions. These tumors represent between 0.8% and 3.7% of all specimens sent to oral pathology laboratories. Ameloblastoma is one of the most frequently encountered tumor arising from odontogenic epithelium characterized as benign, but exhibits locally invasive behavior with high tendency to recur. Odontogenic cysts have varifying origins and these multiple origins represent multiple sources of lining epithelium that is from Cell rests of Malassez, cell rests of Serre. The most commonly occurring odontogenic cysts are radicular, dentigerous and odontogenic keratocyst. Radicular cysts are the most common cysts (65%) and they arise from the epithelial cell rests of Malassez in the periodontal ligament as a sequelae of inflammation which usually follows the death of a dental pulp and represent more than a half of all odontogenic cysts. Dentigerous cysts are the most common developmental cysts (24%). They usually enclose the crown of an unerupted tooth and are attached to its neck. It develops by pericoronal or intraepithelial accumulation of fluid surrounded by reduced enamel epithelium. Odontogenic keratocyst (OKC) is considered to be arising from derivatives from embryonic dental lamina. It compromises approximately 11% of all cyst of the jaws. Some cysts have the potential for aggressive behavior and local recurrence. It is documented that in comparison with parakeratotic type of keratocyst the orthokeratinised type is less aggressive and have lower rate of recurrence. In some situations there is a bud like proliferation of lining epithelium of OKC into the connective tissue capsule of the cyst and is mistaken for as ameloblastoma. Biological behavior of few OKCs are as aggressive as benign neoplasms such as ameloblastoma. OKC is now designated by WHO as a Keratocystic odontogenic tumor (KCOT). The clinically aggressive behavior is a result of properties of the lining epithelial cells and connective tissue capsule. There is also greater proliferative activity in the epithelial cells of inflamed KCOT which could be associated with the disruption of the typical structure of the cystic linings. Neviod basal cell carcinoma syndrome is usually associated with multiple OKCs. Identification of the proliferating activity in such tumors is useful to predict the biological behavior of different lesions. Immunostaining with monoclonal antibody (PC10) against this antigen has been shown to demonstrate the proliferative compartment of normal tissue. Determination of epithelial proliferative activity in these cysts and tumors is a potentially useful means of investigating differences in their biological behavior. Thus this study was done to evaluate the expression of PCNA in odontogenic cysts and ameloblastoma. AIM AND OBJECTIVES: To evaluate and compare PCNA labelling index in 1. Radicular cyst, 2. Odontogenic keratocyst, 3. Dentigerous cyst, 4. Ameloblastoma. Hypothesis: 1. There is increased expression of PCNA in odontogenic keratocyst when compared to radicular and dentigerous cyst. 2. There is no difference in the expression of PCNA when compared between odontogenic keratocyst and ameloblastoma. MATERIALS AND METHODS: Study setting: The study was conducted in the Department of Oral and Maxillofacial Pathology, Ragas Dental College and Hospital, Chennai, using paraffin embedded tissues. A retrospective study was done to evaluate the expression of PCNA using immunohistochemistry in formalin fixed, paraffin embedded tissue specimens (archival tissues) of odontogenic cyst (Radicular, Dentigerous cyst, Odontogenic Keratocyst and Ameloblastoma) using immunohistochemistry in formalin fixed, paraffin embedded archival tissue specimens. Study sample size: The study material comprised of 60 formalin fixed, paraffin embedded tissue specimens archival blocks randomly selected, with adequate clinical details. 1. 15 histopathologically confirmed tissue dentigerous specimens. 2. 15 histopathologically confirmed odontogenic keratocyst tissue specimens. 3. 15 histopathologically confirmed radicular cyst tissue specimens. 4. 15 histopathologically confirmed ameloblastoma tissue specimens. Study subject: The study comprised of 4 groups: This project was approved by Institutional Review Board (IRB) of Ragas Dental College and Hospital, Chennai. Group 1: 15 clinically, radiographically and histologically confirmed cases of dentigerous cyst. Histological criteria: The epithelial lining consist of two to four layers of flattened nonkeratinizing squamous cells and a fibrous connective tissue. The connective tissue wall is frequently composed of very loose fibrous connective tissue or sparsely collagenized myxomatous tissue. Rushton bodies within lining epithelium is seen in the inflamed cyst. Group 2: 15 clinically, radiographically and histologically confirmed cases of keratinizing cystic odontogenic tumor. Histological criteria: Keratinizing cystic odontogenic tumor is characterized by a thin fibrous connective tissue capsule and a lining of corrugated parakeratinized stratified squamous epithelium usually about five to eight cell layers in thickness. Basal layer exhibits a palisaded pattern. Group 3: 15 clinically, radiographically and histologically confirmed cases of radicular cyst. Histological criteria: Radicular cyst is lined by stratified squamous epithelium and consist of a dense fibrous connective tissue capsule with an inflammatory infiltrate containing lymphocytes, neutrophils plasma cells and histocytes. Abundant fibroblasts, lymphocytes and plasma cells can be identified within cystic wall is seen in the long standing (chronic) cases. Group 4: 15 clinically, radiographically and hisologically confirmed cases of ameloblastoma Histological criteria: Ameloblastoma is characterized by sheets and islands of tumor cells in the connective tissue stroma, showing an outer rim of columnar ameloblast with nuclei polarized away from the basement membrane. The centre of these nests is composed of stellate shaped epithelial cells that mimic the stellate reticulum. Methodology: From the paraffin embedded blocks 4 micron thick, sections were cut and used for routine hematoxylin and eosin (H & E) and immunohistochemical (IHC) staining. SUMMARY AND CONCLUSION: A total of 60 cases were included in the study, comprising of 15 cases of dentigerous cyst, (Group I), 15 cases of odontogenic keratocyst (Group II), 15 cases of radicular cyst (Group III) and 15 cases of ameloblastoma (Group IV). 1. The mean ages of patients in group I, group II , group III and group IV were 35.53 ± 7.83, 39.07 ± 7.05, 31.40 ± 8.68 and 40.2±8.55 years respectively 2. In group I (Dentigerous cyst) 73.3% were males and 226.6% were females. 3. In group II (Odontogenic keratocyst) 80% were males and 20% were females. 4. In group III (Radicular cyst) 70% were males and 30% were females. 5. In group IV (Ameloblastoma) 86.6% were males and 13 were females. 6. Among dentigerous cyst, 66.6% of cases exhibited positivity for PCNA and 33.3% of cases were negative. In all positive cases stain was present in basal layer. 7. In odontogenic keratocyst; all cases showed PCNA positivity in the epithelium. The stain was present in the basal and suprabasal layers of epithelium. 8. In radicular cyst, there was 80% of positivity of PCNA expression in the epithelium. All of the positive cases showed staining in the basal layers of the epithelium. 9. All cases of ameloblastoma were positive for PCNA. 10. There was statistical differences in the labeling indices among all the four groups (p=0.004). 11. There was no statistically significant difference in the epithelial staining intensity of PCNA between localization of stain in the basal and suprabasal layers of odontogenic cysts. (p= 0.131). 12. There was no statistical significant difference in the labeling indices of odontogenic keratocyst and ameloblastoma (p=0.520). In the present study, we could not ascertain the PCNA expression as a marker to differentiate between odontogenic keratocysts and ameloblastomas. However, differential markers such as calretenin can be used to differentiate between ameloblastomas and odontogenic keratocysts

Myofibroma of the Gingiva: A Rare Case Report and Literature Review

Myofibromas are benign uncommon fibroblastic tumors of the soft tissue, bone, or internal organs affecting all ages. These lesions histopathologically may mimic many other soft tissue tumors of the oral cavity such as spindle cell tumors of neurogenic and smooth muscle cell origin, thus leading to misdiagnosis and mistreatment. This case report describes a rare benign tumor, which presented as a soft tissue swelling on posterior gingiva. Surgical excision of the lesion was carried out under local anaesthesia. Histopathologic and immunohistochemical examination confirmed the diagnosis of myofibroma. Myofibroma should be included in the clinical differential diagnosis of masses of the oral soft tissues; however immunohistochemical examination is essential to establish an accurate diagnosis