[Frontoethmoidal sinus mucocele as a rare finding in a patient with craniofacial fibrous dysplasia].

Fibrous dysplasia is a benign developmental skeletal disorder characterized by bony expansion secondary to replacement of the medullary cavity by fibroosseous connective tissue. A 16-year-old male patient underwent magnetic resonance imaging for headache, left proptosis, and a thrill over the left temporal artery. T1- and T2-weighted images showed extensive bone involvement of typical low signal intensity in the left hemicalvarium, skull base, and facial bones. Another striking finding was the presence of a frontoethmoidal sinus mucocele, which demonstrated high signal intensity both on T1- and T2-weighted images. The diagnosis was made as fibrous dysplasia after bone biopsy and histopathological evaluation.