Bilateral Parotid Gland Oncocytoma Mimicking Oropharyngeal Cancer Metastasis: A Case Report from a Radiation Oncologist's Perspective.

Background/aim: Parotid oncocytomas typically present as benign, unilateral, slow-growing, painless, and solitary masses that are histologically firm and multilobulated. They are often misdiagnosed as pleomorphic adenomas, hemangiomas, or other forms of oncocytosis. However, in our case, the parotid oncocytomas initially mimicked bilateral parotid gland metastasis of advanced oropharyngeal cancer. Here, we present a case of oropharyngeal cancer with bilateral parotid oncocytomas treated with chemoradiotherapy (CCRT).

Case report: We report the case of a 74-year-old man with a sore throat, neck pain, right earache, oropharyngeal cancer, and bilateral parotid gland oncocytoma. Head and neck computed tomography and magnetic resonance imaging (MRI) showed soft-tissue swelling in the right tonsillar fossa and several enlarged level II neck lymph nodes. MRI revealed enhancing masses in both parotid glands, initially suspected to be metastatic lymph nodes. A biopsy of the right palatine tonsil confirmed squamous cell carcinoma with human papilloma virus-16 positivity. A positron emission tomography scan was performed, and biopsy-proven malignant lesions were observed in the right tonsillar region with metastatic lymph nodes in the right and left neck. Focal hypermetabolism was observed in the parotid glands, suspected to be pathological lesions such as metastatic intra-parotid lymph node or Warthin's tumor. An ultrasonography-guided biopsy of the left parotid gland confirmed an oncocytoma. Based on these results, the patient was scheduled for CCRT. After pathological confirmation of parotid oncocytoma, CCRT was administered, excluding the parotid glands within the radiotherapy field.

Conclusion: This is a case of bilateral parotid gland oncocytoma mimicking oropharyngeal cancer.