Abstract
Chronic expanding hematomas (CEHs) in the retroperitoneal space are rare disease. Since CEHs often develop huge masses, it is difficult to differentiated from malignant tumor. Here, we present a case of CEH in the retroperitoneal space. The lesion exhibited increased activity on 18F-fluordeoxyglucose positron emission tomography (FDG-PET). In the present case, the increased FDG uptake was showed only in the peripheral rim of the mass, and no other abnormal uptake was observed. The findings of our case and previously reported cases suggest that FDG uptake observed only in peripheral rim of the mass might be characteristic findings of CEHs.