Retroperitoneal Chronic Expanding Hematoma Mimicking Malignancy on FDG PET/CT.

A 49-year-old Japanese man had a chief complaint of left hypochondrium pain, and a CT scan revealed a mass in the left retroperitoneal space. CT and MRI scans revealed a hemorrhagic component and surrounding fibrous tissues. FDG PET/CT images showed increased uptake in the peripheral rim of the mass, indicating a malignant tumor. The SUV max was 7.6. We surgically resected the mass. The pathological examination confirmed the diagnosis of chronic expanding hematoma. It is difficult to differentiate CEH from malignant tumors on imaging; this should be recognized as a diagnostic pitfall.