Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma with squamous differentiation in the posterior nasal septum: A rare case report.

RATIONALE: Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is a rare neoplasm characterized by papillary epithelial proliferation and abnormal expression of thyroid transcription factor-1. To our knowledge, squamous differentiation in TL-LGNPPA is an unusual phenomenon, and only 1 case has been reported to date. The tumor occurs mainly on the roof of the nasopharynx. Herein, we report a case of TL-LGNPPA with squamous differentiation located on the posterior nasal septum.

PATIENT CONCERNS: A 45-year-old Chinese women presented to our hospital with a complaint of nasal obstruction for 10 years and the symptom has been getting worse for recent 3 years.

DIAGNOSES: Microscopic examination of the tumor tissue revealed findings typical of TL-LGNPPA, and in addition to the typical components, squamous differentiation could be found in some areas within the fibrovascular cores of the papillary components. Immunohistochemically, the squamous cells were positive for P40 and P63 but negative for thyroid transcription factor-1.

INTERVENTIONS: The patient underwent complete resection of the tumor.

OUTCOMES: Follow up results showed that the patient had no recurrence 41 months after removal of the tumor.

LESSONS: Our report anticipates that, although TL-LGNPPA with squamous differentiation in the posterior nasal septum is rare, this report will expand the existing knowledge associated with TL-LGNPPA.