An unusual case of focal cemento-osseous dysplasia occupying nearly the entire maxillary sinus and arising from adjacent tissue of fused teeth

Cemento-osseous dysplasia (COD) of the jaw is a benign fibro-osseous lesion that is subdivided into three types, periapical, focal, and florid, based on the clinical and radiologic features. Focal COD (FCOD) usually affects the posterior tooth-bearing area or edentulous alveolar process and typically presents as an asymptomatic lesion diagnosed incidentally on dental radiography. In asymptomatic cases, once the diagnosis has been established, invasive treatment is not required. However, routine follow-up is warranted, because some patients develop multiple-site involvement, i.e., florid COD. Symptomatic patients require treatment. We describe the unusual case of a 19-year-old Japanese woman with FCOD in the left maxillary sinus who presented with repeated discomfort in the left side of the cheek. Radiographic examinations showed a mixed radiolucent-radiopaque, well-defined maxillary mass that obliterated nearly the entire left maxillary sinus. We planned to remove the lesion to restore the nasal ostium patency and natural sinus clearance mechanism, because clinical symptoms were considered to result from obliteration of the maxillary sinus by the lesion. The lesion was enucleated via the intraoral approach under general anesthesia. The microscopic examination showed a dense hypocellular sclerotic mass composed of compact bone-like cemento-osseous tissue with irregular lamellar structures. The final diagnosis was determined to be FCOD considering the combination of clinical, radiologic, and histopathological findings. The clinical outcome was satisfactory without postoperative infection or complications.