Early colon cancers detected by FDG-pet: a report of two cases with immunohistochemical investigation.

Increased glucose uptake is one of the metabolic characteristics of tumor cells. 18F-fluorodeoxyglucose (FDG)-positron emission tomography (FDG-PET), a technique that is used widely to study this altered glucose metabolism in tumors, allows the detection of various types of malignancy. We present herein two cases of early colon cancers detected incidentally by FDG-PET. The technique was used as part of the screening examinations for preoperative staging, and for postoperative follow-up. In both cases, the lesions were removed by colonoscopic polypectomy, with no complications. Moreover, we confirmed the existence of altered glucose metabolism in the resected specimen by immunohistochemical staining using an antibody raised against Glut1. Immunohistochemically, Glut1 was expressed in vitro in both of the lesions, supporting the positive FDG-PET result obtained in vivo. To our knowledge, this is the first report to describe in vitro Glut1 expression and in vivo tumor detection using FDG-PET in colorectal carcinoma.