A surprising inverse correlation between the degree of malignancy and the level of FDG uptake in a colon tumor.

A 66-year-old woman was hospitalized because of hematochezia. She underwent sigmoidoscopy, and a cauliflower tumor measuring 3.0 X 1.5 cm was found at the 25-cm level. A biopsy was performed and the tumor was diagnosed assigmoid adenocarcinoma. The CEA value was 12.1. An FDG PET scan was performed for staging. A lesion showing increased FDG uptake was seen in the ascending colon, and one showing much less uptake was seen in the sigmoid colon. At colonoscopy, a polypoid tumor was seen that measured 3 cm was sampled at the 60-cm level. The polypoid tumor was diagnosed as villotubular adenoma. An anterior resection for sigmoid cancer and a colostomy with wedge resection for an ascending colon adenoma were performed.