ODONTOGENIC FIBROMA IN SPRAGUE-DAWLEY RATS - A REPORT OF 2 CASES

Two cases of odontogenic fibroma occurring in aged Sprague-Dawley rats are described. Both neoplasms were associated with a maxillary inciso r and had identical histomorphological features. They were composed of solid proliferations of primitive, dental pulp-like mesenchyme separa ted by areas of collagenization. Small strands and islands of mainly u ndifferentiated odontogenic epithelium immunostaining for keratins wer e scattered throughout both tumours. As a further characteristic, the lesions contained small foci of mineralization which were either cemen tum-like or resembled dysplastic dentin. The odontogenic fibroma repre sents a further type of odontogenic tumour in rats, which due to its t ypical histomorphology, can easily be differentiated from other odonto genic tumours such as ameloblastic odontoma or ameloblastoma.