Incidental Finding of COVID-19 Lung Infection in 18F-FDG PET/CT: What Should We Do?

We report the case of an asymptomatic (no fever, no cough, no dyspnea) 80-year-old woman who had an F-FDG PET/CT scan for initial staging of Lieberkühnian adenocarcinoma located on anal canal. Chest analysis incidentally revealed bilateral diffuse patchy ground-glass opacity with mild increasing F-FDG uptake, consistent with incidental COVID-19 infection finding during the March 2020 pandemic. The infection was confirmed by reverse transcription-polymerase chain reaction. It led us to improve patient flow and to undertake broader measures to avoid patient clinical issues and potential disease spreading.

PET/CT acquisition was performed 1 hour after intravenous infusion of 145 MBq of 18F-FDG. A, 18F-FDG PET/CT maximum intensity projection showed an intense uptake (SUVmax 12.8) in anal canal primary neoplasm (black arrow) and increasing uptake in right lung corresponding in axial PET/CT slices to subpleural ground-glass opacity with 18F-FDG increasing uptake in right upper lobe (SUVmax of 2.4) (B, C), associated with patchy, rounded, diffuse, ground-glass opacity with mild FDG uptake (D, E). This incidental lung lesion finding, even in an asymptomatic patient, was consistent with typical appearance of COVID-19 infection during the March 2020 pandemic.[1-5] There was no evidence of lymph node FDG uptake compared with some prior reported cases.[6,7] The infection was confirmed by reverse transcription–polymerase chain reaction on nasopharyngeal swab collection.

Following this event, we took measures to decrease the risk of disease spreading in our department. They are synthetized in this algorithm. Every patient must be screened for COVID-19 infection risk before and upon entering in the unit. Patients suspicious for COVID-19 infection have to wear surgical mask and to be isolated, combined with transmission droplets-based precautions for the medical staff.[8] As chest CT has high sensitivity to detect COVID infection,[9] we recommend to analyze chest area before patient leaves camera’s bed. This allows taking hygienic measures (particularly specific COVID camera disinfection) to protect the following patients.[10] For that purpose, it is necessary to increase time between examinations. In case of suspected COVID-19 infection scan, it is warmly recommended to notify medical and paramedical staff in order to adapt patient’s care (including transfer and reverse transcription–polymerase chain reaction test) and hygienic measures. Patient and contact cases must be warned to strictly adhere to isolation rules and for self-monitoring in case of ambulatory care in asymptomatic form. More generally, it is recommended to cancel nonurgent investigations and to limit contact with other patients.[11] These recommendations are all the more important to follow as there is an increased risk of COVID infection (1% vs 0.29%) and more frequent complication (39% vs 8%) in the cancer patient population.[12]