Immunohistochemical features of proliferative marker and basement membrane components of two feline inductive odontogenic tumours.

Feline inductive odontogenic tumour (FIOT) is a rare and interesting odontogenic neoplasm in which the odontogenic epithelium has inductive potential to form aggregated foci of dental pulp-like mesenchymal cells. Two male cats aged 11 and 10 months presented with nasal swelling and a left maxillary mass. Histopathologically, the masses consisted of non-encapsulated invasive neoplasms exhibiting proliferation of epithelial and mesenchymal components with local infiltration into the maxillary bone in both cases. The epithelial component formed islands, anastomosing strands, and solid sheets of polygonal epithelial cells. Occasionally, these cells formed circular aggregates, resembling the cap stage of odontogenesis. Type IV collagen and laminin were constantly positive around the foci of epithelial cells, and Ki-67 positive indices were extremely low; therefore, these findings consistent with the benign clinical presentation of FIOT.