Carcinoma arising in oncocytic Schneiderian papilloma.

Two men aged 54 and 73 years, respectively, had oncocytic Schneiderian papilloma (OSP) containing synchronous carcinoma at the time of first biopsy. In both cases, invasive carcinoma involved a small proportion of excised tissue and was in continuity with dysplastic surface epithelium. Our cases document that the epithelial component of OSP can undergo malignant transformation. The focal involvement of OSP with carcinoma underscores the need to examine all excised tissue microscopically.