Imaging features of parotid gland oncocytoma: a case series study

Reports regarding the imaging findings of parotid gland oncocytoma are limited and prospective definitive diagnosis is difficult. This case series is aimed at furthering the knowledge of imaging for parotid gland oncocytoma.

Seven patients with pathologically confirmed parotid gland oncocytoma were identified between January, 2016 and August, 2020. They were subjected to computed tomography, magnetic resonance imaging or ultrasound. Imaging features of lesions were retrospectively analyzed and documented by a senior radiologist.

Among the 7 recruited parotid gland oncocytoma patients, 4 were males and 3 were females. They were aged between 47 and 87 years with a median age of 63 years. The range of maximum diameter of the mass was about 1.6-4.5 cm, with the median size being 3.5 cm. All cases were unilateral single masses. Three patients had their parotid gland oncocytoma located in the deep lobe of the parotid gland and 4 patients had their parotid gland oncocytoma located in the superficial lobe. Most lesions exhibited a clear boundary and irregular shapes or lobulated, and contain cystic components. Local pain was the most common clinical manifestation. Most of the lesions exhibited a hypoechoic mass on ultrasound, soft tissue density on computed tomography, iso to hypointense signal on T1 weighted imaging, slightly hypersignal on T2 weighted imaging, while contrast-enhanced computed tomography, magnetic resonance imaging, and ultrasound showed avid enhancement.

Parotid gland oncocytomas usually exhibit a clear boundary to surrounding parotid tissue, lobulated or irregular shape and avid enhancement, sometimes accompanied with cystic components. Diagnosis of parotid gland oncocytoma should be considered when these features are encountered in clinical practice.