Immunohistochemical characteristics of thyroid-like low-grade nasopharyngeal papillary adenocarcinoma: A case report and review

Background:Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is a rare nasopharyngeal malignant tumor that is easy to misdiagnose. Immunohistochemistry plays an indispensable role in distinguishing TL-LGNPPA from other malignancies. However, there is no article to summarize the immunohistochemical characteristics of TL-LGNPPA. Herein, we report a case of TL-LGNPPA and present the immunohistochemical results reported in the Chinese literature. Methods:An electronic search of the CNKI (China National Knowledge Infrastructure) database was performed. From our literature survey, 53 cases of TL-LGNPPA (including the case described in this report) have been identified in China. We summarize the Chinese literature's clinical characteristics, immunohistochemical results, treatments, and prognosis of 53 cases. Results:Based on our literature survey, 53 cases of TL-LGNPPA (including the case described in this report) have been reported in China. We found TL-LGNPPA and papillary thyroid carcinoma were positive for TTF-1 and CK19. TL-LGNPPA was negative for TG and PAX-8, whereas papillary thyroid carcinoma was positive for TG and PAX-8. However, negative expression of TTF-1 and positive expression of TG were also found in some TL-LGNPPA cases. Our literature survey found that all TL-LGNPPA cases were negative for PAX-8.Therefore, we suggest that simultaneous immunohistochemical determination of TTF-1 and CK19, as well as TG and PAX-8, can increase the diagnostic accuracy of TL-LGNPPA. Conclusion:The 4th edition of the World Health Organization Classification of Head and Neck Tumors (WHO-HNT) indicates that NPPA with positive expression of cytokeratin 19 (CK19) and TTF-1 and negative expression of TG is called TL-LGNPPA.