Clinicopathological Features of Low-Grade Thyroid-like Nasopharyngeal Papillary Adenocarcinoma.

Primary low-grade thyroid-like papillary adenocarcinomas are extremely rare neoplasms that generally originate in the nasopharynx. Here, we describe a novel case of a 15-year-old Chinese girl who was diagnosed with low-grade thyroid-like papillary adenocarcinoma, including a brief review of the literature to reveal the clinicopathological features of low-grade thyroid-like nasopharyngeal papillary adenocarcinoma.Immunohistochemistry was used to evaluate the expression of pan-cytokeratin (CKpan), cytokeratin (CK) 7, thyroid transcription factor 1 (TTF-1), vimentin, epithelial membrane antigen (EMA), thyroglobulin, CD15, S100, P40, CK20, CDX-2, glial fibrillary acidic protein (GFAP), and Ki-67. Additionally, in situ hybridization investigation was utilized to identify the presence of small Epstein-Barr virus (EBV)-encoded RNA.Histopathological analysis revealed florid proliferation of papillary structures lined by columnar epithelial cells with fibrovascular cores. Immunohistochemically, the neoplastic cells were positive for CKpan, CK7, TTF-1, vimentin, and EMA, but negative for thyroglobulin, CD15, S100, P40, CK20, CDX-2, and GFAP. The Ki-67-labeling index reached 5% in the most concentrated spot. In situ hybridization for EBV was negative.Due to the distinct rarity of low-grade thyroid-like papillary adenocarcinomaswith a favorable clinical outcome, a nationwide effort to raise public awareness of this neoplasm is required.