Thyroid-Like Low-Grade Nasopharyngeal Papillary Adenocarcinoma with Biphasic Histology

Rusella Mirza,Guillermo A Herrera,Nestor Dela Cruz

doi:10.1155/2020/3275916

Abstract

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is a rare primary adenocarcinoma of nasopharynx. The immunohistochemical pattern of this tumor is similar to that of papillary thyroid carcinoma making this neoplasm a challenging diagnosis. A case of TL-LGNPPA with biphasic morphology is presented. The removed tumor from the nasopharynx exhibited a polypoid appearance. Microscopically, it was composed of papillary structures admixed with a few solid areas of spindle cells. The papillae were lined by columnar epithelium. Both the epithelium and the spindle cells were strongly positive for TTF-1 and CK19 and negative for CK5/6, S-100, and thyroglobulin. Cellular atypia, necrosis, and high mitotic rate were absent. Ki67 was less than 2% in the neoplastic cells. No local recurrence or distant metastasis was reported after 12 months of follow-up. Caution should be taken to differentiate TL-LGPPA from other TTF-1-positive neoplasms, especially papillary thyroid carcinoma, as the prognosis for these two tumors is entirely different.

Highlights

Primary adenocarcinoma of the nasopharynx is extremely rare, representing less than 0.5% of all primary carcinomas of the nasopharynx [1,2,3]
This tumor is composed of papillary structures, and the papillae are lined with columnar or cuboidal epithelium
Low-grade nasopharyngeal papillary adenocarcinoma was first reported by Wenig et al in 1988 [6]

Summary

Introduction

Primary adenocarcinoma of the nasopharynx is extremely rare, representing less than 0.5% of all primary carcinomas of the nasopharynx [1,2,3]. According to the recent WHO classification, thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is considered a variant of nasopharyngeal papillary adenocarcinoma [3]. Immunostains have defined two subsets of low-grade nasopharyngeal papillary adenocarcinoma. The other subtype is thyroid-like which shows strong positivity for TTF-1 and CK19. TL-LGPPA is extremely rare with only about 40 cases reported in English literature. This tumor is composed of papillary structures, and the papillae are lined with columnar or cuboidal epithelium. A bi-phasic pattern with spindle cell population has been reported in very few cases [4, 5]

Case Report

Discussion

Findings

Conclusion