In addition, the role of FDG PET / CT as a problem-solving tool in patients on follow-up for a treated CRC, has been increasing in the setting of unexplained elevation of carcinoembryonic antigen and equivocal findings on conventional imaging modalities.[6] In this pictorial essay, we illustrate the spectrum of recurrence of CRC and the role of FDG PET / CT in its detection, characterization, and treatment response evaluation. This evidence concerns the gene CEACAM5 and colorectal carcinoma.