A 66-year-old-man underwent a PET/CT scan after a biochemical relapse for a prostate cancer previously treated with a laparoscopic surgical procedure which revealed a focal uptake in the posterior wall of sigmoid colon. The biopsy demonstrated a colon cancer with mucinous differentiation producing a shift in clinical priority. To the best of our knowledge this is the first report in the English literature describing the detection by (18)F-choline PET/CT of a colorectal cancer with mucinous differentiation.