Immunohistochemical Evaluation of Cytokeratin 19 and Calretinin in Odontogenic Cysts and Tumors

Aesha, - (2011) Immunohistochemical Evaluation of Cytokeratin 19 and Calretinin in Odontogenic Cysts and Tumors. Masters thesis, Ragas Dental College & Hospital, Chennai.


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INTRODUCTION: Odontogenic cysts and tumors are a diverse group of lesions arising from the odontogenic apparatus, which is responsible for tooth development under physiologic conditions. Odontogenic tumors, which arise from odontogenic epithelium, odontogenic ectomesenchyme or both constitute a group of heterogeneous lesions that range from hamartomatous or non-neoplastic tissue proliferations to malignant neoplasms with metastatic capabilities. Ameloblastoma is the most frequently encountered tumor arising from odonotgenic epithelium and is characterized by a benign but locally invasive behavior with high tendency to recur. Odontogenic cysts include three main groups of cysts, whose epithelial linings are thought to have differing origins. The epithelial lining of radicular cyst is presumed to arise from epithelial rests of Malassez, that of dentigerous cyst from reduced enamel epithelium and that of odontogenic keratocysts from dental lamina or its remnants. The odontogenic keratocyst is a destructive cystic lesion that has a propensity for recurrence. The term Keratocystic odontogenic tumor is given because of its aggressive nature, rapid growth rate and high recurrence rate. Ameloblastomas are usually lined by a variable epithelium ranging from one that has typical ameloblastic characteristics to one that is metaplastic and which appears completely nondescript consisting of several layers of non keratinizing squamous cells. Overlapping clinical and radiographic features further add to this diagnostic difficulty. Many techniques have been used in an attempt to distinguish odontogenic cysts from ameloblastoma. Although the cyst linings may have lost their typical ameloblastic features, the cells retain their immunophenotypic characteristics like continued expression of cytokeratin 19 and calretinin. Cytokeratins (CKs) are specific intermediate filaments of epithelial cells. In humans, they comprise a complex family of atleast 20 different polypeptides. Based on their charges, immunoreactivity and amino acid sequence, they fall into two subfamilies: acidic proteins with low molecular weight and basic proteins with high molecular weight. Cytoplasmic intermediate filaments are involved in differentiation of mammalian cells. The expression pattern of intermediate filaments has been investigated in normal and neoplastic human cells including oral epithelial cells, odontogenic epithelia, tumors and cysts. These investigators hypothesize that intermediate filaments expression patterns are characteristic for each kind of cells. Cytokeratin 19 is the smallest known acidic type of cytokeratin, having molecular mass of 40kD. It is not paired in epithelial cells .It is expressed in all kinds of odontogenic epithelial cells in developing tooth germs and in neoplastic epithelial cells in some odontogenic tumors. It is also detected in cell rests of Malassez, Serre’s and odontogenic cyst lining. Calretinin is a calcium binding protein of 29 kilodalton (29kDa) and is a member of the large family of EF-hand proteins. EF- hand proteins are characterized by a peculiar amino acid sequence that folds up into a helix-loop-helix which acts as the calcium binding site; calretinin contains six such EF-hands stretches. Calretinin is widely expressed in neural tissue and is also a specific marker of mesothelial cells, mast cells, cutaneous mastocytomas, neural elements of the tooth pulp and periodontal ligament. The viscerosensory nerve fibers of oral and pharyngeal tissues have also demonstrated the expression of calretinin in rats8.This calcium-binding protein may be a specific marker of ameloblastic tissues and may be an important diagnostic aid in differential diagnosis of cystic odontogenic lesions and ameloblastic tumors. This study was done to evaluate the expression of cytokeratin 19 and calretinin in odontogenic cysts and ameloblastoma. AIMS AND OBJECTIVES: To assess cytokeratin 19 and calretinin expression from archival paraffin embedded sections of radicular cyst, dentigerous cyst, odontogenic keratocyst and ameloblastoma by immunohistochemistry. HYPOTHESIS: 1. Cytokeratin 19 is expressed in all odontogenic cysts and ameloblastoma. 2. Calretinin is expressed in ameloblastoma and not in odontogenic cysts. Study Setting: The study was conducted in the Department of Oral and Maxillofacial Pathology, Ragas Dental College and Hospital, Chennai. A retrospective study was done to evaluate the expression of calretinin and cytokeratin19 using immunohistochemistry in formalin fixed, paraffin embedded tissue specimens of odontogenic cysts (radicular cysts, dentigerous cysts, odontogenic keratocysts) and ameloblastoma. Sample Size: The study material comprised of 60 formalin fixed, paraffin embedded tissue specimens (archival blocks). Group I: Fifteen clinically, radiographically and histologically confirmed dentigerous cysts. Histological criteria: The epithelial lining consists of two to four layers of flattened nonkeratinising squamous cells and a fibrous connective tissue capsule. Group II: Fifteen clinically, radiographically and histologically confirmed odontogenic keratocysts. Histological criteria: Odontogenic keratocyst is characterized by a thin fibrous connective tissue capsule and a lining of corrugated parakeratinized/orthokeratinized stratified squamous epithelium usually about five to eight cell layers in thickness. Basal layer exhibits a palisaded pattern. Group III: Fifteen clinically, radiographically and histologically confirmed radicular cysts. Histological criteria: Radicular cyst is lined by stratified squamous epithelium and consists of a dense fibrous connective tissue capsule with a mixed inflammatory infiltrate. Group IV: Fifteen clinically, radiographically and histologically confirmed ameloblastoma specimens. Histological criteria: Odontogenic epithelium proliferating in the form of islands or follicles or strands, embedded in a mature connective tissue stroma. SUMMARY: 1. A total of 60 cases were included in our 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). The mean ages of study groups in group I, II, III, 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, 73% were males and 27% were females. In Group II, 80% were males and 20% were females. In Group III, 67% were males and 33% were females. In Group IV, 87% were males and 13% were females. 3. In Group I, none of the dentigerous cyst cases showed Calretinin stain. Cytokeratin 19 showed 13.3% of mild staining and 6.6% showed moderate staining pattern. 4. In Group II, 6.7% cases of odontogenic keratocyst showed mild staining and 6.7% showed moderate staining for Calretinin. Cytokeratin 19 did not exhibit any staining characteristic. 5. In Group III, there was no immunoexpression for calretinin and cytokeratin 19. 6. In Group IV, all the cases showed immunoexpression for calretinin. 6.7% of the cases showed moderate staining for cytokeratin 19. 7. In comparison of staining intensity of Group II and IV the p value 0.004 was considered to be statistically significant. CONCLUSION: In conclusion, the results of the current study show that calretinin could be a immunohistochemical marker for neoplastic ameloblastic epithelium and it may be an important diagnostic aid in the differential diagnosis of cystic odontogenic lesions and ameloblastic tumors. Cytokeratin 19 is a marker of simple epithelia. Absence of cytokeratin 19 in odontogenic keratocyst could be due to the nature of epithelium or give to different differentiating pattern of epithelium.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Immunohistochemical Evaluation ; Cytokeratin 19 ; Calretinin ; Odontogenic Cysts and Tumors.
Subjects: DENTAL > Oral Pathology and Microbiology
Depositing User: Kambaraman B
Date Deposited: 12 May 2018 04:54
Last Modified: 12 May 2018 04:54

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