Objective    To study the clinical manifestations

pathologic features

and differential diagnosis of odontogenic adenoid tumor（OAT）.     Methods    Eight OAT patients admitted to Department of Stomatology in our hospital from January 2000 to June 2010 were enrolled in this study. Their clinical

imaging

and immunohistochemical data were analyzed and its related literature was reviewed.     Results    Of the 8 OAT patients (3 males and 5 females) at the age of 14-27 years (mean 20 years)

3 were diagnosed with OAT in upper maxilla and 5 with OAT in lower maxilla. Their main clinical manifestations were local painless swelling and facial asymmetric malformation. The radiographic features included monolocular radiolucent shadow

opaque calcified particles

and tooth-like mass with an increased density. The main pathological lesion was OAT with a diameter of 4.0 cm and an intact capsule

characterized by cystic lesion

grit-like nodules on the cystic wall

tremelloid liquid

and non-growth out teeth in the cyst. The tumor was mainly composed of epithelial cells and a small amount of interstitial tissue. Solid parenchyma cell nest

tubular structure

ethmoid or cribriform structure

homogeneous substances and feosin-addicted calcified foci in different sizes and irregular shapes were formed in proliferated tumor cells. Immunohistochemical staining was positive for CK

vimentin and PAS.     Conclusion    OAT is a special kind of odontogenic benign tumors occurring mainly in upper maxilla and can be misdiagnosed as adamantinoma or dentigerous cyst. Its diagnosis can be established by biopsy before operation and freezing during operation

which benefits the selection of its surgical procedure.