Lymphadenopathy resulting from acute hepatitis C infection mimicking metastatic breast carcinoma on FDG PET/CT.

We report a case documenting fluorodeoxyglucose (FDG) accumulation in upper abdominal lymph nodes resulting from acute hepatitis C infection. A 42-year-old African-American female with a history of metastatic breast carcinoma was found to have hypermetabolic porta hepatic, peripancreatic, and paraaortic lymphadenopathy and hypermetabolism in the spleen on a surveillance FDG positron emission tomography/computed tomography (PET/CT) scan. Concurrently, she was diagnosed with acute hepatitis C infection. Antiviral therapy was not recommended secondary to the low level of detectable virus at the time of diagnosis. Her breast cancer therapy regimen was continued unaltered. FDG PET/CT scan was repeated 2 months later as a result of concern that the hypermetabolic lymph nodes represented metastatic disease; however, the scan revealed complete resolution of the previously abnormal findings. The resolution of the lymphadenopathy and the patient's clinical course led to the conclusion that the most likely explanation for the FDG PET/CT findings was inflammation secondary to acute hepatitis C infection and not metastatic breast carcinoma. Inflammatory and infectious processes accumulate FDG, occasionally resulting in false-positives for malignancy. Infected macrophages in the lymph nodes draining the liver in this case and stimulation of a cellular immune response by the hepatitis C virus, with resultant cytokine production by cytotoxic and T-helper cells, offer possible explanations for the findings seen on FDG PET/CT in this case. This case highlights the importance of clinical history and laboratory correlation for the proper interpretation of FDG PET scans.