59 year old man with history of colon cancer (T4N0M0 – transverse colon mass with invasion of anterior abdominal wall, s/p extended right hemicolectomy with en block resection of proximal transverse colon and anterior abdominal wall) presented with fluid collection in the abdomen and pelvis, seen on a CT scan. Whole body PET-CT was done to assess for recurrent disease. Liver function tests were within normal limits at time of scan. PET-CT case of the month (04/10): Hypermetabolic Focal Fat Sparing

PET images show diffuse increased uptake in the left lobe of liver (SUVmax 3.0) and relatively decreased uptake in the right lobe of liver (SUV max 2.2). The corresponding CT images show that the low attenuation right lobe of liver (from fatty infiltration) is well demarcated from the normal looking left lobe of liver. Fat infiltrated liver is likely hypometabolic compared to the spared liver tissue. Focal fat sparing has been shown to mimic metastatic disease on PET-CT imaging (1).

1. Focal Fat Spared Area in the Liver Masquerading as Hepatic Metastasis on F-18 FDG PET Imaging. Purandare, N C.; Rangarajan, Venkatesh; Rajnish, Anshu; Shah, Sneha; Arora, Abhishek; Pathak, Sujata. Clinical Nuclear Medicine. 33(11):802-805, November 2008.