Parotid incidentalomas on positron emission tomography: what is their clinical significance? Ramona-Rita Barbara a , Davina Pawaroo a , Clare Beadsmoore a , Nabil Hujairi b and David Newman a Objective and aim The increased use of PET/CT in cancer staging has resulted in more incidental findings in unexpected locations, making this a challenge for the radiologist interpreting the study. Our aim was to determine the frequency of parotid incidentalomas and to assess the ability of PET/CT to characterize them. Patients and methods At the Norfolk and Norwich University Trust, in between October 2010 to October 2015, 4044 patients had a PET/CT examination. The issued clinical reports that contained the word ‘parotid’ were traced and all patients selected for this study had no known or suspected parotid disease before the PET/CT scan. Results The prevalence of parotid incidentalomas was 1.73%; higher than expected as was the mean age of our study group. Ten per cent of patients had no focal lesion identified on subsequent ultrasound. Thirty-two per cent of patients had a biopsy which showed that the majority of these findings were benign and 13% had metastatic deposits, with the primary carcinoma in these cases being neuroendocrine colon carcinoma, non-Hodgkin’s lymphoma and melanoma. Conclusion The most common benign salivary tumour in our study was Warthin’s tumour and the majority of these patients had a primary lung carcinoma. Given that the main predisposing factor for both pathologies is smoking, potentially this suggests an association between the incidence of primary lung carcinoma and Warthin’s tumour. Ten (14%) patients in our study had a standardized uptake value of below 3.2 (using the VUE Point HD algorithm). These patients had either no identifiable lesion on ultrasound or no malignant features on histology; therefore, we propose that a cut-off of 3.2 on PET/CT could be used to differentiate between physiological or benign uptake from malignant fluorine-18-fluorodeoxyglucose uptake in the parotid gland. Nucl Med Commun 40:264–269 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved. Nuclear Medicine Communications 2019, 40:264–269 Keywords: parotid incidentalomas, positron emission tomography/computed tomography, Warthin’s tumour a Norwich Radiology Academy, The Cotman Centre, Norwich and b Royal Marsden Hospital, London, UK Correspondence to Ramona-Rita Barbara, MD (Malta), Norwich Radiology Academy, Colney Lane, The Cotman Centre, Norwich NR4 7UB, UK Tel: + 44 1603 286 140; e-mails: ramonasultana@gmail.com, ramona-rita.sultana@nnuh.nhs.uk Received 12 July 2018 Revised 7 November 2018 Accepted 10 November 2018 Introduction The use of whole-body fluorine-18-fluorodeoxyglucose ( 18 F-FDG) PET/CT for cancer staging has resulted in an increased detection rate of synchronous primary tumours [1]. During the interpretation of a PET/CT, radiologists are challenged by findings of abnormal incidental foci of 18 F-FDG uptake in unexpected locations [2]. The manner in which this phenomenon is further investigated will be significant in the subsequent management and staging of the disease. This nonphysiological uptake in locations that is not typical for metastatic spread of the underlying malignancy may be due to an unrelated benign process or a second primary tumour [2]. Parotid gland incidentalomas are focal areas of 18 F-FDG accumulation in patients without a prior history of the parotid disease [3]. These foci are most commonly due to benign lesions such as Warthin’s tumour, but they can also be caused by metastatic lymph nodes or malignant tumours [3]. The aim of this study was to determine the frequency of unexpected focal uptake of 18 F-FDG on PET/CT in the parotid glands and to assess the ability of PET/CT to characterize these lesions. To our knowledge, this is the first study looking at the prevalence of parotid inci- dentalomas detected on PET/CT in the UK. Patients and methods The cases for this study were retrospectively selected from a population of patients who had a whole-body PET/CT study at the Norfolk and Norwich University Hospital from October 2010 to October 2015. The clinical reports of PET/CT studies that contained the word ‘parotid’ were selected for this study. Patients with a previous clinical history of a diagnosed primary parotid tumour or metastases before the PET/CT scan were excluded from the study. Therefore, all patients selected for this study had no known or suspected parotid disease before the PET/CT examination. Ethics approval Original article 0143-3636 Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/MNM.0000000000000961 Copyright r 2019 Wolters Kluwer Health, Inc. All rights reserved.