Abstract
Fibrous dysplasia is a slow growing fibro-osseous tumor, which is infrequent in craniofacial location and very rarely found in paranasal sinuses. Its occurrence is usually in children and young adolescents. The complications common in this location are related to the sinus ostia obstruction, like sinusitis or mucocele formation. Aneurysmal bone cyst formation has also been reported. We present a case of frontoethmoid fibrous dysplasia which extends to the nasal cavity and extraaxial frontal region. The peculiarity about the case is its association with the intradiploic CSF cyst formation, which to best of our knowledge has never been reported before.