ABSTRACT
To determine calretinin expression by immunohistochernistry in ameloblastoma and keratocystic odontogenic tumors [KCOT] and to document the use of calretinin as a differentiating marker between the two lesions. A cross sectional study conducted on previously diagnosed cases of ameloblastoma and Keratocystic odontogenic tumour. Armed forces Institute of Pathology, Rawalpindi Pakistan and duration was one year. [Sep 2009 - Aug 2010]. Twenty cases each of Ameloblastoma and KCOT were retrieved from the record files along with their paraffin embedded blocks. Histological features of all the cases were reviewed on freshly prepared slides and a fresh diagnosis made regardless of the previous diagnosis. The immunohistochemical marker, Calretinin, was applied on both types of cases using the avidin-biotinylated peroxidase complex method.The results were interpreted. In the cases of Ameloblastoma the epithelial tumour nests showed positivity for Calretinin expression. In 85% cases; intense and diffuse staining was observed in more than 80% of the stellate reticulum like cells while 15% cases showed focal and moderate staining patterns. On the other hand KCOT showed contrary results as none of epithelial lining expressed positive staining for Calretinin, [p<0.001]. Calretinin can be used as a useful marker for Ameloblastoma and can be used to differentiate KCOT from Ameloblastoma