Pleomorphic adenoma with extensive oncocytic change in the parotid gland: a case report and review.

Background: Pleomorphic adenoma (PA) is the most common benign tumor of the salivary glands, but rarely shows extensive oncocytic metaplasia. Extensive oncocytic metaplasia within PA is rarely encountered and may closely mimic malignant neoplasms, creating significant diagnostic challenges for clinicians and pathologists. This uncommon histologic variant can potentially influence clinical decision-making processes and subsequent patient management strategies. Case Description: A 54-year-old male presented with a painless, slowly enlarging mass in the left parotid gland, which had persisted for two years. Imaging studies revealed a poorly demarcated 2.6 cm mass involving both the superficial and deep lobes of the parotid gland. Fine needle aspiration biopsy suggested oncocytic changes within PA. The patient underwent total parotidectomy with preservation of the facial nerve and reconstruction using an artificial dermal matrix. Histopathological analysis confirmed PA with extensive oncocytic metaplasia and negative surgical margins. Postoperatively, the patient experienced transient weakness of the buccal branch of the facial nerve, which resolved completely within 15 days. No recurrence was observed during the 12-month follow-up period. Conclusions: Recognition of this oncocytic variant of PA requires a multidisciplinary diagnostic approach to avoid misdiagnosis and overtreatment. Total parotidectomy with facial nerve preservation provides favorable functional and oncologic outcomes. Awareness of this rare variant and proper diagnostic evaluation are essential for optimal patient management.