Pitfalls in interpretation of FDG PET/CT: Septic pulmonary emboli mimicking metastases in a case of gastric carcinoma

Inflammatory lesions may sometimes show intense tracer uptake and mimic neoplastic lesions on (18) F-fluoro-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). We report one such false positive case on FDG PET/CT, where septic pulmonary emboli (SPE) mimicked pulmonary metastases. A 45-year-old man with stomach cancer had an indwelling central venous catheter (CVC) in situ while on neoadjuvant chemotherapy. He underwent FDG PET/CT scan for response assessment and the images revealed multiple, intensely FDG avid, peripheral, lung nodules with feeding vessels, which were suspicious for pulmonary metastases. A day later, the patient developed fever with chills and his blood culture showed bacterial growth (Enterobacter cloacae). A provisional diagnosis of SPE from an infected CVC was made. Chemotherapy was withheld, CVC removed, and the catheter tip was sent for bacterial culture. Following a 4-week course of antibiotic treatment, the patient became afebrile. Culture from the CVC tip grew the same organism, as was seen earlier in the patient's blood culture, thus pin-pointing the source of infection in our case. Diagnosis of SPE was clinched when follow-up CT chest done after completion of antibiotic course showed complete resolution of the lung lesions.