Since both APC and Msh2 mutations can cause genomic instability by themselves (Apc: CIN; Msh2: MIN), a role of K-ras mutation in the gastrointestinal (GI) tract may be at least to exacerbate already existing genomic instability, although K-ras mutation alone may be insufficient to generate tumor aneuploidy. This evidence concerns the gene MSH2 and neoplasm.