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Background:Amelogenins are the major enamel proteins that play a major role in the biomineralization and structural organization of enamel. Aberrations of enamel-related proteins are thought to be involved in oncogenesis of odontogenic epithelium. The expression of amelogenin is possibly an indicator of differentiation of epithelial cells in the odontogenic lesions.Aims and Objectives:The present study aimed to observe the expression of amelogenin immunohistochemically in various odontogenic lesions.Materials and Methods:Paraffin sections of 40 odontogenic lesions were stained immunohistochemically with amelogenin antibodies. The positivity, pattern and intensity of expression of the amelogenin antibody were assessed, graded and statistically compared between groups of odontogenic cysts and tumors.Results:Almost all the odontogenic lesions expressed amelogenin in the epithelial component with the exception of an ameloblastic carcinoma. Differing grades of intensity and pattern were seen between the cysts and tumors. Intensity of expression was uniformly prominent in all odontogenic lesions with hard tissue formation. Statistical analysis however did not indicate significant differences between the two groups.Conclusion:The expression of amelogenin antibody is ubiquitous in odontogenic tissues and can be used as a definitive marker for identification of odontogenic epithelium.

The odontogenic keratocyst (OKC) has recently been reclassified by the WHO (2005), as keratocystic odontogenic tumor (KCOT) based on clinical, histological and immunohistochemical parameters. KCOT more commonly occurs in the mandible and cases involving the maxilla are infrequent. We report an unusual and rare case of a KCOT of the maxilla in a middle-aged individual with extensive involvement and displacement of the maxillary third molar to the zygomatic region. A discussion of the parameters involved in the reclassification of the lesion as a tumor is presented alongwith a review of literature.