Carcinoma Ex Combined Inverted and Oncocytic Types Sinonasal Papilloma with Multifocal Severe Dysplasia: A Case Report

Sinonasal papillomas, also called Schneiderian papillomas, are uncommon benign epithelial tumors arising from the pseudostratified ciliated sinonasal mucosa. Three subtypes of sinonasal papillomas have been described, namely exophytic papilloma, inverted papilloma, and oncocytic papilloma. These papillomas usually have a favorable prognosis, however, frequent recurrences and local aggressiveness has been observed. These may undergo malignant transformation in rare instances. We report a case of a 70-year-old male with multiple co-morbidities presenting with nasal obstruction and bleeding for 3 months. CT and MRI sinuses demonstrated a polypoid mass within the right nasal cavity extending into the nasopharynx, likely arising from the right maxillary sinus. Histopathology revealed a diagnosis of carcinoma (poorly differentiated, NOS) ex combined inverted and oncocytic types sinonasal papilloma (Schneiderian papilloma) with multifocal severe dysplasia (carcinoma in situ). Importance of correct diagnosis lies in the fact that these tumors show recurrence and malignant transformation, thus, requiring long-term follow-up. Keywords: Schneiderian papilloma; Sinonasal papilloma; Malignant transformation; Radiotherapy; Oncocytic