Benign osteoblastoma of the ethmoid sinus.

Osteoblastoma is categorized as a benign bone-forming tumor, which occurs rarely in the craniofacial region. We report a case of osteoblastoma developed in the nasal cavity and ethmoid sinus in a 14-year-old girl whose chief symptom was nasal obstruction and exophthalmos on the right side. CT revealed the lesion having the same density as bone and a ground-glass border, expanding to the nasal and paranasal cavities. Complete removal was accomplished under endoscopic view, although the tumor was removed piece by piece. Histologic inspection showed exuberant osteoid trabeculae and immature bone formation by osteoblasts with vascularized connective tissue. We diagnosed the tumor as osteoblastoma based on the clinical presentation and the size of the tumor. No recurrence was evident at the 1-year follow-up visit.