GCC has been shown to be expressed in various GI cancers, including 98% of colorectal, 68% of stomach, 64% of pancreatic, and 59% of esophageal cancers; furthermore, GCC expression was found to be higher in colorectal tumors than in matched healthy tissues [7–9], and GCC-positive status was maintained throughout tumor progression based on results from immunohistochemistry (IHC) assays of matched colorectal cancer and liver metastasis cases [7]. This evidence concerns the gene GUCY2C and colorectal neoplasm.