[Giant osteoma with intracranial extension filling sinonasal cavity: a rare case].

Osteomas are the most frequently observed benign bone tumors of paranasal sinuses. Although they are generally detected by chance during radiological analyses, they may create severe complications after intracranial extension. While computed tomography findings play a key role to differentiate osteoma from other osseous lesions of paranasal sinus, magnetic resonance imaging identifies extension to surrounding structures and possible complications. Osteoma was detected in a 28-year-old female patient who admitted with complaints of headache and difficulty in breathing. Patient was operated after diagnosis; however, we were unable to remove the mass totally due to its location and size. In this article, we report, to our knowledge, the largest defined osteoma case in the literature to date, with ethmoid sinus origin, orbital, nasal cavity and intracranial extension, accompanied with distinctive computed tomography and magnetic resonance imaging findings.