RESUMO
Inverted Papilloma is the most common form of sinonasal Papilloma and accounts for 50-78% of sinonasal Papilloma and estimated to represent 0.5-4% of sinonasal tumors, with greatest potential for local invasion and malignant transformation. Recurrence rate of the disease is about 14 to 75% depending on the treatment modality. It is associated with malignancies usually squamous cell carcinoma in 3 to 24% of cases. The patient is a 43-year old man with chief complaint of trismus and pus drainage on his cheek from six months ago who came to Taleghani hospital in Tehran. Radiographic examinations revealed a mass in his right maxillary sinus involving the medial and lateral sinus walls but the orbital floor was intact. And cortical perforation was seen in Water's radiographic and CT scan. Incision biopsy was done from the palatal ulcer. According to histopathologic features we diagnosed a squamous cell carcinoma on a previous inverted Papilloma. Inverted papilloma has a great potential of recurrence and malignant transformation so a complete surgery and prolonged follow up is highly recommended. In this article patient didn't agree complete surgical removal lesion and attending follow up sessions