Thyroid-Like Low-Grade Nasopharyngeal Papillary Adenocarcinoma.

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is a rare entity. Patients often present with complaints of nasal fullness, obstruction, and epistaxis. It may be confused with metastatic papillary thyroid carcinoma due to its histologic similarity and overlapping immunohistochemical studies, but it is important to distinguish between the two because of differing treatment modalities and prognosis. A significant difference between the two is that despite both entities demonstrating TTF-1 positivity, TL-LGNPPA usually does not stain for thyroglobulin. TL-LGNPPA exhibits indolent growth, with no incidence of metastasis or recurrence after surgical excision.