Multiple Oncocytomas of Bilateral Parotid Glands: A Case Report

Significance Statement

Oncocytomas are rare benign tumors, usually present as slow-growing, painless lesions. Their clinical presentation and radiological imaging features can be confused with other tumoral lesions of the parotid gland.

Introduction

The parotid gland is the most common localization of oncocytoma. However, it can be seen in any other salivary gland. Patients usually present with slow-growing painless parotid masses. In some reported case series, it has been stated that it is more common in the female gender.^1,2

Some radiological methods such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) can be used for the diagnosis of oncocytoma. Other salivary gland tumors may also have imaging features similar to oncocytoma and may not be clearly differentiated radiologically.

The CT imaging features of the oncocytoma include well-defined, sometimes bilaterally and generally homogenous contrast enhancement masses. A well-defined contrast-enhancing mass is an important diagnostic feature for benign parotid malignancies such as Warthin tumor and basal cell adenomas. However, several clues can be found in differentiating oncocytoma from other benign parotid gland tumors. Oncocytomas present with a well-circumscribed mass with homogeneous contrast enhancement, often with a non-enhancing central cleft secondary to the central scar. In addition, oncocytomas may have included non-enhancing cystic components. ² Although Warthin tumors can be frequently demonstrated with the cystic components, they have no central scar. Moreover, the contrast uptake pattern of the masses after contrast agent application may reveal features that can be used in the differential diagnosis of the lesions. Pleomorphic adenoma which is the most common tumor of the parotid gland typically shows minimal or no enhancement in the early post-contrast scan phase. ³ Conversely, oncocytoma demonstrates mostly increased enhancement in the early phase.

Fine-needle aspiration biopsy is the first choice for the diagnosis of salivary gland tumors. Contrary to the satisfactory results on the other salivary gland tumor, fine-needle aspiration biopsy has a low diagnostic rate for the diagnosis of the oncocytoma. It has been reported at 29%. ⁴ The surgical treatment option, total or superficial parathyroidectomy, for oncocytomas may vary depending on the location of the lesions.

Case Presentation

An 80-year-old female patient attended the Ear, Nose & Throat clinic with a complaint of swelling in front of both ears for several months. On the physical examination, there were palpable masses in both parotid gland regions. The patient did not complain of pain during palpation. On the other hand, there was no palpable lymphadenopathy.

Contrast-enhanced CT scan demonstrated multiple solid masses on both parotid glands. These masses had homogenous contrast enhancement (Figures 1A-1C). The size of the largest lesion was measured 15 × 18 millimeters in the left parotid gland.

Figure 1.

Consecutive post-contrast coronal CT scans (A-C) show multiple homogenous contrast-enhanced solid lesions (arrows) in both the parotid glands.

Excisional biopsy was performed on the patient for diagnosis. As a result of histopathological examination, the patient was diagnosed with oncocytoma.

Conclusion

Bilateral and multiple demonstrations of parotid gland oncocytomas are rare. It should be kept in mind that it may present as multiple masses in both parotid glands and may contain a cystic component in patients presenting with a painless mass in advanced ages. It is necessary to review the central scar finding and contrast uptake pattern, which may be helpful in the differential diagnosis.