A Rare Case Report: Nasopharyngeal Pleomorphic Adenoma

Pleomorphic adenoma is the most common type of benign tumors of salivary glands. Pleomorphic adenoma commonly arises from the parotid gland and could also be located in larynx, pharynx, trachea, and lips. Pleomorphic adenoma rarely occurs in nasopharynx and may present with nasal onstruction. In adult patients, it can be confused with nasopharynx cancers. The risk of recurrence and squamous metaplasia should be kept in mind. The gold standard treatment method is transnasal endoscopic total excision.


INTRODUCTION
Salivary gland tumors constitute about 5 % of all head and neck tumors (1). Pleomorphic adenoma (PA) which is also known as benign mixt tumor is the most common type of benign tumor of salivary glands. PA commonly arises from the parotid gland and may also be formed in the submandibular gland and minor salivary glands (1,2).
Minor salivary gland originated tumors are frequently seen in palate, they may also be present in locations such as the larynx, pharynx, trachea, and lips. However, pleomorphic adenoma cases with nasopharyngeal location are rarely encountered in the literature (3,4).
The purpose of this article is to present a case of PA, a rare tumor originating from the nasopharynx.

CASE REPORT
A 40-year-old male patient referred to our clinic with a complaint of nasal obstruction. Oropharyngeal examination was normal. No pathological finding was detected in anterior rhinoscopy. In the endoscopic examination, a mass of approximately 2x2 cm was observed, filling the nasopharyngeal cavity almost completely. Other otorhinolaryngological examinations were all normal. Nasopharyngeal MRI showed a mass of 26x23x26 mm with heterogeneous contrast and minimal pathological diffusion restriction (figure 1). Punch biopsies from different zones were obtained under local anesthesia. Pathological examination result was reported as "upper respiratory tract mucosa characterized by chronic inflammation". An endoscopic tumor excision was performed under general anesthesia and the mass was totally excised (figure 2).
The mixed tumor (pleomorphic adenoma) was reported in the pathological examination. In addition, an expanding growth pattern has been reported with no apparent capsule, vascular invasion, or neural invasion.

DISCUSSION
Salivary gland neoplasms usually are encountered in major salivary glands. About 75% of the PAs occur in the parotid gland. PAs comprise 65% of all neoplasms originating from the parotid gland (5). Only 10% of PAs are formed in the minor salivary glands. Depending on where the small salivary glands are located, PA can occur in different locations. PA can be seen on soft and hard palate, trachea, larynx, upper lip and floor of mouth (6).PA is also known as benign mixed tumor that include myoepithelial and epithelial cells. PA is surrounded by a false capsule which usually shows pseudopod extensions into the salivary gland tissue (7). PA often appears as an asymptomatic mass with a slow growth pattern in the parotid gland. It is more common in females (64,5%) and often seen during the 4th and 5th decades (4). Nasal septum deviation and chronic sinusitis are the most common causes of nasal obstruction. However, patients with masses in the nasopharynx may also complain with nasal obstruction. When a nasopharyngeal mass is detected in childhood, an adenoid vegetation is usually suspected, while adult patients are suspected of nasopharyngeal cancer. Moreover, benign masses such as Thornwaldt cysts, mucus retention cysts, and branchial cysts may also be detected in nasopharynx (8).
PA located in the nasopharynx is a very rare condition. A total of fewer than 10 cases have been reported to the date. Patients with Nasopharyngeal PA are often referred with complaints of nasal congestion. The second most common complaint is serous otitis media (SOM) due to Eustachian tube dysfunction (9).
The treatment of PA is surgical total excision. Transnasal endoscopic approach is the main treatment method for PA located in nasopharynx. Total excision of the mass is recommended to avoid from the risk of recurrence. In this case, we performed transnasal endoscopic total tumor excision. GMJ 2020; 31: 674-676 Ceylan et al.
Rarely, squamous metaplasia can be observed. PA with squamous metaplasia could be misdiagnosed as Squamous cell carcinoma so pathologist should keep minor salivary gland tumors of the nasopharynx in mind (10).

CONCLUSION
PA rarely occurs in nasopharynx and may present with nasal obstruction. In adult patients, it can be confused with nasopharynx cancers. The risk of recurrence and squamous metaplasia should be kept in mind. The gold standard treatment method is transnasal endoscopic total excision.