A 70-year-old man presented with a change in mental status. He had undergone a nephrectomy for renal cell carcinoma in 1991 and chemoradiation therapy for metastases to the hip and spine in 1999. His disease had been in remission since 2000. A noninfused computed tomographic scan of his head showed a soft tissue density in the left ethmoid region surrounded by bone remodeling. No intracranial metastases were seen. Chest and abdominal radiographs did not reveal any metastases. The patient did not have any nasal symptoms. Rigid nasal endoscopy revealed an isolated smooth, circumscribed, nonpolypoid, solid mass within the left middle meatus. There was no evidence of pus. An infused maxillofacial computed tomogram further defined the soft tissue as a 2-cm, rim-enhancing, expansile lesion within the left ethmoid sinus extending inferiorly into the nasal cavity and demonstrating bone remodeling without bone destruction (Figure 1). A small osteoid osteoma was seen in the right ethmoid sinus. The patient's clinical status was improving. Because of the unusual nature of the lesion, an incisional biopsy was performed endoscopically without difficulty.