Case report

Transitional features of benign and malignant oncocytic tumors: Report of two cases

Deep lobe of the parotid gland is a rare localisation of head and neck tumors and most of them are pleomorphic adenoma. We encountered a 76-year-old woman with deep lobe parotid gland oncocytic neoplasms (synchronous oncocytoma and multifocal nodular oncocytic hyperplasia), but without any complaints. The patient was operated for larynx carcinoma four years ago. A deep lobe parotid gland lesion was detected during radiological evaluation of her middle ear cholesteatoma. A near total parotidectomy was performed. Oncocytoma is an uncommon salivary gland tumor and generally occurs in the superficial lobe of parotid gland of older patients. Multifocal nodular oncocytic hyperplasia is an unusual parotid gland lesion that accounts for 0.1% of parotid tumors. Computed tomography, magnetic resonance imaging, FNA and sialoscintigraphy may be helpful for evaluating parotid gland oncocytomas. Acinic cell carcinoma and clear cell carcinoma were the main differential diagnosis of oncocytoma. Surgical removal is the treatment of choice and total parotidectomy is suggested for deep lobe parotid gland oncocytomas. Recurrences are unusual for oncocytoma. Long-term follow up is necessary for multinodular cases. Parotid gland space occupying lesions may necessitate further emphasis regarding the fact that either second primary or a metastatic lesion may be found in especially a previously noted head and neck carcinoma patient.

Background: Oncocytic neoplasms of the parotid gland are a rare collection of salivary gland tumors that include oncocytosis, oncocytoma, and oncocytic carcinoma. Mounting evidence has linked the presence of oncocytes to acquired mitochondrial dysfunction. Objectives: The study goals were to further delineate this poorly understood group of salivary gland tumors and to search for genetic alterations indicative of mitochondrial dysfunction. Methods: Cases were identified by search of the surgical pathology archival files from 1984 through 2000. Corresponding medical records were reviewed. Tumor mitochondrial DNA (mtDNA) was evaluated for mtDNA mutations within the control region (C-tract). Results: Twenty-one parotid oncocytic neoplasms were identified. Oncocytoma was the most frequent morphology (62%), followed by oncocytosis (28.5%) and oncocytic carcinoma (9.5%). One specimen displayed synchronous oncocytic morphologies (oncocytoma, oncocytosis, and oncocytic metaplasia). One oncocytoma specimen displayed the mtDNA C-tract alteration. Conclusions: Oncocytic neoplasia of the parotid gland is a rare form of salivary gland disease with obscure etiology. The presence of multiple oncocytic morphologies in a single specimen is suggestive of transition between forms. Although oncocytic tumorigenesis secondary to acquired mitochondrial dysfunction is a plausible mechanism, few of these tumors actually harbor mtDNA alterations within the control region. (Otolaryngol Head Neck Surg 2002;126:657-662.)