Primordial odontogenic tumor: report of 2 new cases.

Primordial odontogenic tumor (POT) is a recently described benign odontogenic tumor, with only 16 cases reported in the literature. We present 2 new cases of POT affecting the mandible. Case 1 is that of 12-year-old girl with an asymptomatic, slow-growing mass, causing facial asymmetry. Radiography showed a well-defined unilocular radiolucency surrounding an impacted second premolar. Case 2 is that of a 13-year-old girl with a mass involving the crown of the unerupted third molar and showing similar radiographic features. Microscopically, both lesions were composed of variably cellular fibromyxoid tissue surrounded by thin ameloblastic epithelium, with stellate reticulum-like areas, but no mineralized tissue, yielding the diagnosis of POT. Immunohistochemical analysis showed diffuse expression of CK14 in epithelial cells, whereas CK19 was expressed mainly in the basal layer. Syndecan-1 (CD138) was expressed in the stellate-like regions and in the subepithelial zone. Both patients were treated surgically, with no signs of recurrence seen after 15 and 60 months, respectively.