Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma: A case report

Abstract

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is a rare neoplasm characterized by morphological analogy to papillary thyroid carcinoma and abnormal expression of thyroid transcription factor-1 (TTF-1). We herein report a rare case of TL-LGNPPA with a review of its clinical, morphological and immunohistochemical characteristics. The patient was a 25-year-old Japanese woman complaining of a 2-year history of fever of unknown origin. There were no remarkable physical findings and the laboratory tests, including C-reactive protein levels, were normal. Laryngoscopy, magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography identified a pedunculated mass at the roof of the nasopharynx. Histologically, the tumour exhibited papillary growth of cuboidal or columnar epithelium. Tubular architecture and a spindle cell component were also observed focally. Some tumour cells exhibited intranuclear cytoplasmic inclusions. Immunohistochemically, the neoplastic cells were positive for TTF-1, cytokeratin 7 and vimentin, but were negative for thyroglobulin. The Ki-67 labelling index (MIB-1 index) reached 5% in the most concentrated spot. The patient had neither local recurrence nor distant metastasis 3 years after removal of the tumour. In conclusion, TL-LGNPPA should be included it in the differential diagnosis of fever of unknown origin.

Thyroid-like low-grade papillary adenocarcinoma of nasopharynx

“…The most common IHC pattern of TL-LGNPPA tumour cells is TTF-1 positivity and TG negativity, which is negative for TTF-1 and diffusely positive for TG in PTC. Such finding has been reported in all previously reported cases of TL-LGNPPA as well as our patient 2–9. These two neoplasms have some similar IHC patterns including CK7 expression and vimentin 2.…”

“…Such finding has been reported in all previously reported cases of TL-LGNPPA as well as our patient 2–9. These two neoplasms have some similar IHC patterns including CK7 expression and vimentin 2. These findings were observed in the patient reported by Horino et al 2.…”

“…These two neoplasms have some similar IHC patterns including CK7 expression and vimentin 2. These findings were observed in the patient reported by Horino et al 2. IHC staining for PAX-8 is another useful method to identify the TL-LGNPPA from metastatic PTC as it is positive in tumours from thyroid origin 13.…”

“…Thyroid-like LNPPA is an extremely rare tumour of nasopharynx with only a limited number of cases reported in the literature 2–9. NPPA includes 0.38%–0.48% of all malignant nasopharyngeal neoplasms 10.…”

“…Low-grade nasopharyngeal primary papillary adenocarcinoma (LGNPPA) is a subgroup of traditional nasopharyngeal adenocarcinoma 1. Among them, there is a small group of tumours that morphologically are like thyroid papillary carcinoma with thyroid transcription factor 1 (TTF-1) expression, so named as thyroid-like LGNPPA (TL-LGNPPA) 2…”