Pericardial mucinous adenocarcinoma on 18F-FDG PET/CT. 
A 56-year-old woman presented a history of left chest discomfort for 6 months.  A prior CT revealed pericardial thickening, and malignancy cannot be excluded.  For this reason, an FDG PET/CT scan was performed, which revealed abnormal activity inside the pericardium.  The pathologic examination results after surgery demonstrated a mucinous adenocarcinoma.