Aggressive inverted papilloma with intracranial invasion and short malignization time.

Inverted papillomas (IP) are considered benign lesions with a prevalence up to 4% among all sinunasal tumors; however, invasive growth and varying tendency for malignization are reported in literature. We report the case of a 69-year-old woman suffering from a large, aggressively growing IP invading the orbit, skull base, and frontal lobe of the brain. Within only 3 months' time the papilloma showed transformation into an invasive carcinoma, leaving surgical therapy in vain due to explosive recurrence. Intracranial and intraorbital expansion by IP is possible despite histology not showing signs of malignancy initially. In "regular" IP close endoscopic follow-up is mandatory to not overlook recurrence harboring malignancy.