Adenomatoid odontogenic tumor with fibro-osseous reaction in the surrounding tissue

Adenomatoid odontogenic tumor (AOT) is a relatively rare odontogenic tumor that is exclusively odontogenic epithelium in origin. We present a rare case of an AOT in a patient with fibro-osseous reaction in the surrounding tissue. A 22-year-old woman complained of gradual swelling of the right maxillary for 1 month. Radiography showed a well-defined radiolucent lesion with root resorption of the involved teeth. The biopsy revealed a primarily cystic lesion surrounded by a solid portion. Microscopically, the cystic part mainly consisted of epithelial cells organized in solid nodules, whorls, and rosettes, typically characteristic of AOT. But the surrounding solid portion showed cellular fibroconnective tissue stroma with prominent calcified spherules corresponding to ossicles and cementicles, characteristic of ossifying fibroma. The presence of a prominent fibro-osseous reaction in our case is unique. To our knowledge, these findings have not been observed in the previous reports of AOT. It could well represent a cellular cystic wall with metaplastic ossification, rather than a benign fibro-osseous neoplasm such as ossifying fibroma. The tumor had no recurrence after local resection at 5-year follow-up.