Low-Grade, Nonintestinal Nonsalivary Sinonasal Adenocarcinoma Associated With an Exophytic Schneiderian Papilloma: A Case Report.

Sinonasal adenocarcinoma is a rare tumor of the head and neck accounting for 10% to 20% of all primary malignancies of the nose and paranasal sinuses. There tumors are classified as salivary, intestinal and nonintestinal, nonsalivary. Low-grade nonintestinal nonsalivary are rare tumors whose diagnosis is essentially that of exclusion. Here we present the first case of one such tumor associated with an exophyic Schneiderian papilloma. A 71-year-old retired aerospace engineer presented with a 1-year history of severe nasal obstruction. Endoscopy and compted tomography imaging demonstrated a polypoid lesion occupying his entire right nasal cavity extending into and filling the nasopharynx. Biopsy suggested adenocarcinoma, at least in situ and the patient subsequently underwent complete resection. Pathologic evaluation demonstrated polypoid tumor consistent with a low-grade papillary adenocarcinoma with micropapillary architecture associated with a small amount of residual exophytic Schneiderian papilloma. Immunohistochemistry revealed diffuse expression of CK7, CK 5/6, and S100 protein in tumor cells. Expression of p63 was seen in basal cells only. Tumor cells did not show expression of CK20, CDX2 (intestinal markers), mammaglobin, GATA3 (salivary markers), PAX8, WT1, nor estrogen, progesterone, or androgen receptors confirming its nonintestinal nonsalivary differentiation.