# The Salivary Tumor That Lost Its Way: A Case Report of Sinonasal Pleomorphic Adenoma

## TL;DR

A rare case of nasal pleomorphic adenoma, a salivary gland tumor, was diagnosed through histology and RNA sequencing in a 46-year-old man.

## Contribution

This case report highlights the rare occurrence of pleomorphic adenoma in the nasal cavity and its diagnosis using RNA sequencing.

## Key findings

- Histology showed biphasic ductal epithelial-like and myoepithelial architecture consistent with pleomorphic adenoma.
- RNA sequencing detected an NCALD::PLAG1 fusion, confirming a salivary cell origin.
- The case emphasizes the importance of considering pleomorphic adenoma in nasal obstruction or mass differential diagnosis.

## Abstract

Pleomorphic adenoma (PA) is a benign tumour that most commonly arises in the salivary glands but can occur in other sites. Occurrence in the nasal cavity is rare, arising from minor salivary tissue. A 46-year-old man with primary ciliary dyskinesia and type 2 diabetes presented with bilateral nasal obstruction and chronic rhinosinusitis. Examination showed bilateral nasal polyposis, with the right one being more obstructive. Computed tomography (CT) demonstrated bilateral diffuse pansinus mucosal thickening with polypoidal transformation. The patient underwent bilateral endoscopic sinus surgery. Nasal polyps were sent for a routine histological examination. Histology revealed sheet-like fascicular growth of uniform ovoid-spindled cells with biphasic ductal epithelial-like and myoepithelial architecture, in keeping with PA. Targeted RNA sequencing detected an NCALD::PLAG1 fusion, supporting a salivary cell origin, with PLAG1 alterations characteristic of PA. PA of the nasal cavity, although rare, should be considered in the differential diagnosis of unilateral nasal obstruction or mass. Surgical excision remains the definitive treatment. Long-term clinical surveillance is advised, considering the risk of later recurrence or malignant transformation.