S-100 Protein Immunoreactivity of Calcifying/calcified Areas in Odontogenic Tumors

Odontogenic tumors could be classified into noncalcified tumor such as ameloblastoma; ameloblastic fibroma and squamous odontogenic tumor; and calcified tumors such as calcifying epithelial odontogenic tumor (CEOT), calcifying odontogenic cysts (COC) and adenomatoid odontogenic tumor (AOT). S-100 protein, the EF hand Ca2+ binding protein, is involved in a variety of cellular regulations, including Ca2+ signaling process. S-100 protein immunoreactivity was observed in CEOT, COC and AOT, and it was expressed either in the focus of calcification or ghost cells and in acellular homogenous areas suggesting precalcification where calcification process may occur. S-100 protein staining was also expressed in tumor epithelial cells in CEOT (1/3) and compact tumor cells in cords and strand structures of AOT. No S-100 protein immunoreactivity was observed in odontogenic tumor cells where they fail to demonstrate areas of calcification within the tumor mass; i.e., ameloblastoma, squamous odontogenic tumors and ameloblastic fibroma lacked S-100 protein staining, except for granular cells of ameloblastoma which were positive for S-100 protein. Odontogenic epithelial islands localized at periphery of the focus in odontoma expressed S-100 protein where the connective tissue cells were also reactive for S-100, suggesting that induction of dental hard tissues or calcification may be associated with the presence of immunoreactive S-100 protein.