Signaling pathways enable cells to communicate between the cell surface and the nucleus, thereby responding to extracellular signals with changes in behavior. Mutations in signaling pathway genes, such as KRASand NRAS, lead to abnormal activation, often inducing increased proliferation, lack of differentiation, and resistance to apoptosis. These are often found in subclonal cellular fractions, indicating that they arise from a late clonal event in disease evolution.