Oncocytoma of the Parotid Gland: A Potential False-Positive Finding on 18F-FDG PET

WEB This is a Web exclusive article. ET with 18F-FDG has been successfully used for the diagnosis, management, and follow-up of many malignant tumors. PET is particularly useful for staging of head and neck tumors and for detecting recurrence [1]. Its utility in other settings, however, such as detection of non–squamous cell cancer of the head and neck and differentiating benign salivary gland tumors from malignant ones, is limited [2, 3]. This lack of usefulness may partly be explained by the poor anatomic localization of PET combined with variable physiologic uptake of FDG in the head and neck. These factors decrease the specificity of PET for head and neck cancer and thus increase the rate of false-positive findings. Combined PET/CT scanners, which fuse the functional data of PET with the anatomic data of CT, have shown promise in the evaluation of cancer of the head and neck [4]. Non–squamous cell cancer of the head and neck, particularly salivary gland tumors, however, have not been studied extensively with either PET or combined PET/CT. In cases that have been studied, the variable uptake from salivary gland tumors often causes false-negative results [4–6]. In addition, some benign tumors of the salivary glands, particularly Warthin’s tumor, show focal FDG uptake leading to false-positive results [2]. These false-positive findings reduce the utility of PET in differentiating benign salivary gland tumors from malignant tumors. We report a case of a benign parotid oncocytoma that had marked FDG avidity on PET/CT.