Oncocytic sinonasal papilloma in the nasal and paranasal sinuses: a case report and review of the literature.

Oncocytic sinonasal papilloma (OSP) is an uncommon, benign neoplasm characterized by papillary growths arising from the Schneiderian mucosa of the nasal and paranasal sinuses. OSP accounts for about 3-6% of all sinonasal papillomas (SPs), and clinically is often confused with inverted sinonasal papilloma (incidence 73%). Although SP shares some of the clinical characteristics of OSP, the pathogenesis differs and it is very important to distinguish between them. Here we present a case of OSP in the nasal and paranasal sinuses of a 67-year-old Japanese male, who complained of persistent left-sided nasal obstruction. A benign nasal paranasal tumor was diagnosed, and endoscopic sinus surgery was performed. Histopathologically, the tumor cells exhibited an exophytic and endophytic growth pattern, composed of multilayered eosinophilic columnar epithelium with finely granular cytoplasm, and forming microcysts filled with mucin or microabscesses. The epithelium was PTAH-positive, and showed positivity for cytokeratin-7 with oncocytic features. A review of the literature revealed 166 cases of OSP in the nasal and paranasal sinuses, with an overall recurrence rate of about 15%. Here we report a case of OSP in the nasal and paranasal sinuses for which PTAH staining specific for oncocytes was useful, together with a review of the relevant literature.