Inverted Schneiderian papilloma is an uncommon benign tumor that presents tendency to recur and propensity to be associated with malignancy in approximately 10% of the cases. Some of these lesions are isolated in the maxillary sinus, and predominantly affect white males with mean age of 50 years. We report a case of squamous cell carcinoma arising from inverted Schneiderian papilloma in the maxillary sinus extending to the mouth. The patient was submitted to extraction of a maxillary molar tooth four months before the exacerbation of the symptoms of nasal airway obstruction and facial enlargement. Computed tomography scan revealed a sinonasal mass causing opacification of the right maxillary sinus with destruction of the lateral nasal wall and maxillary sinus floor. The patient was referred to an oncology center for treatment and died from tumor progression one year after the cancer was diagnosed. The intention of this report is to alert dentists to include the inverted Schneiderian papilloma, either associated with squamous cell carcinoma, or not, in the differential diagnosis of maxillary sinus tumors with aggressive behavior, which may extend to the oral cavity or involve roots of teeth.