Low-Grade Papillary Schneiderian Carcinoma of the Sinonasal Cavity and Temporal Bone

Objectives: The aim of this study was to further characterize a newly described neoplasm, low-grade papillary Schneiderian carcinoma, occurring simultaneously in the sinonasal cavity and mastoid. Additionally, the authors review the only 2 similar cases within the literature and describe the common clinical features, radiographic findings, and pathologic characteristics of this exceptionally rare disease process. Methods: Chart review for single patient, review of literature. Results: The patient presented with bilateral nasal obstruction. Computed tomography revealed a left sinonasal mass with skull base hyperostosis, and follow-up magnetic resonance imaging showed a concomitant olfactory groove meningioma. Examination showed a bilateral, completely obstructing sinonasal mass with skip areas, and biopsy confirmed inverted papilloma (human papilloma virus strains 16 and 18 indeterminate). The patient underwent bilateral endoscopic sinus surgery, left medial maxillectomy, and left partial nasopharyngectomy. Given her multifocal disease, she was advised that she would require additional excision, but was lost to follow up. One year later she developed acute left facial paralysis. Magnetic resonance imaging demonstrated an enhancing mass in the left mastoid with enhancement along the Eustachian tube in addition to her known recurrent sinonasal disease. Simultaneous endoscopic sinus surgery and mastoidectomy were performed. Polypoid tissue was removed from the nasopharynx, mesotympanum, epitympanum, and retrofacial air cells. Immunohistochemistry showed that cells stained positive for p63 and dermCK and negative for synaptophysin. Morphologically, cells were bland, without classic stromal invasion, retaining their smooth, cystic, and papillary features, despite their increased depth within the tissue. Upon further review and consultation with an outside pathologist, a diagnosis of low-grade papillary Schneiderian carcinoma was made. The patient was referred for radiation therapy and is disease free at 3-month follow-up, with return of her facial function. Conclusions: This case represents the first report of concurrent low-grade papillary Schneiderian carcinoma of both the nasal cavity and mastoid. It emphasizes the importance of recognizing this new entity through pathologic analysis and suspecting it when the clinical course does not follow an expected pattern.