Inflammatory pseudotumour of the maxillary sinus mimicking malignancy. Inflammatory pseudotumours of the paranasal sinuses are rare entities and can be easily confused with aggressive malignant tumours. In this report we describe the characteristic behavior of inflammatory pseudotumours in the maxillary sinus. We present a case of a 47-year-old Caucasian woman, who presented in our ENT department because of progressive nasal obstruction, epistaxis, and epiphora. The clinical as well as the radiological findings suggested a maxillary sinus neoplasm, most probably of malignant nature. The histopathological examination showed an inflammatory pseudotumour of the maxillary sinus with polypoid structure and no signs of malignancy.