An intraosseous sclerosing odontogenic tumor predominantly composed of epithelial cells: relation to (so-called) sclerosing odontogenic carcinoma and epithelial-rich central odontogenic fibroma.

We report a case of an asymptomatic sclerosing odontogenic tumor in a 31-year-old woman. Radiologically, the tumor was well circumscribed, was predominantly radiolucent, and had a peripheral sclerotic margin. Histopathologically, the tumor showed small clusters, strands, and cords of small to medium-sized epithelial tumor cells in a sclerotic collagenous stroma. Immunohistochemically, the tumor cells were positive for broad-spectrum cytokeratins (CKs) (CK7, CK5/6, CK19, and CAM 5.2) and p63. Membranous staining for E-cadherin was present. There was weak to moderate nuclear expression of p16 in 30% of cells. Rare tumor cells were positive for p53. Progesterone receptors were expressed in about 60% of the tumor cells. The proliferative activity (Ki-67) was approximately 2%. A molecular genetic (fluorescence in situ hybridization) study showed no EWSR1 (EWS RNA-binding protein 1) gene rearrangement. No recurrence or metastatic events have been documented at 1-year follow-up. This tumor represents a classification dilemma mainly between epithelial-rich central odontogenic fibroma and the so-called sclerosing odontogenic carcinoma.