Atypical Presentation of COVID-19 Incidentally Detected at 18F-FDG PET/CT in an Asymptomatic Oncological Patient.

The incidence of COVID-19, a severe acute respiratory syndrome caused by SARS-CoV-2, is rapidly growing worldwide. In this pandemic period, the chance of incidental pulmonary findings suggestive of COVID-19 at F-FDG PET/CT in asymptomatic oncological patients is not negligible. To suspect COVID-19 is more demanding whether its presentation is atypical. We describe the incidental PET/CT detection of an F-FDG-avid isolated centrilobular pulmonary consolidation in an asymptomatic lymphoma patient, which later resulted in an unexpected and atypical COVID-19 presentation. The nuclear medicine physicians should be prepared to suspect COVID-19 even in asymptomatic patients presenting with a "far-from-COVID-19" finding at PET/CT.

A 59-year-old man with diffuse large B-cell lymphoma on whom an 18F-FDG PET/CT was performed for immunochemotherapy response evaluation on March 18, 2020, 27 days after COVID-19 outbreak in Italy. Along with partial metabolic response, PET maximum intensity projection image (A) revealed a focal uptake area in the middle field of the right lung, corresponding on axial images (B, low-dose free-breathing coregistered CT; C, fused PET/CT; D, PET only) to a metabolically active (SUVmax 3.3) isolated centrilobular consolidation in the middle lung lobe surrounded by a faint ground-glass opacity (GGO) (maximum diameter 28 mm), without any other parenchymal alterations detectable bilaterally at coregistered CT (E). At that time, the patient was considered at low risk of SARS-CoV-2,[1] being completely asymptomatic and denying suspected expositions to infected people. Based on clinical and morphofunctional characteristics, the PET/CT finding was interpreted as a nonspecific pneumonia at an early phase, as frequently occurring during chemotherapy. A subsequent clinical/radiological evaluation was suggested. On March 30, still asymptomatic without specific medication, the patient underwent a chest x-ray for revaluation, showing bilateral parenchymal consolidations, highly suggestive of viral pneumonia. He suddenly was tested for SARS-CoV-2 through nasopharyngeal swab, resulting as positive, and he was quarantined at home.

Soon after, the patient developed fever, cough, and intense dyspnea. On April 4, he went to a local accident and emergency department, where a chest CT was performed: axial images showed widespread multiple bilateral GGOs and consolidations with air bronchogram in both upper and lower lung fields with predominant peripheral distribution, concordant with typical bilateral COVID-19 pneumonia.[2,3] After several days of assisted ventilation with continuative positive airway pressure and multidrug treatment (including steroids, hydroxychloroquine, tocilizumab, levofloxacin, azithromycin, low-molecular-weight heparin, antiplatelet, lopinavir/ritonavir), patient’s disease status improved. To the best of our knowledge, this is the first reported case of an atypical presentation of a confirmed COVID-19 pneumonia as unilateral isolated and relatively small 18F-FDG–avid consolidation in an asymptomatic oncological patient incidentally detected at PET/CT. Growing literature reports on symptomatic and asymptomatic[4-18] oncological patients with incidental 18F-FDG–avid pulmonary findings highly suggestive of COVID-19, although presenting with more common multiple bilateral GGOs and consolidations. Our case highlighted that atypical PET/CT presentation of COVID-19 in asymptomatic oncological patients, appearing as in our case, is the most challenging issue for nuclear medicine physicians. Indeed, oncological patients undergoing PET/CT may present with pulmonary malignancies (eg, lung cancer, lymphoma), but often copresenting pulmonary treatment-related inflammatory/infective processes (eg, nonspecific pneumonia). At PET/CT, these conditions could show similar morphofunctional appearance, but considered atypical for COVID-19. Therefore, in such unexpected COVID-19 case, to suspect the most likely diagnosis, although incorrect, is highly probable. Now more than ever, it is of paramount importance to avoid delay in COVID-19 diagnosis. Consequently, we should consider any new-onset pulmonary lesion as a possible COVID-19 manifestation, until proven otherwise. Therefore, a SARS-CoV-2 test may be considered even for an asymptomatic patient at low risk of SARS-CoV-2 infection and presenting with an apparently “far-from-COVID-19” finding at 18F-FDG PET/CT, aiming to promptly reach a definitive diagnosis, reduce the viral spread, and early indicate appropriate therapeutic management.