The "seed and soil" hypothesis suggests that metastatic sites are not random but are influenced by the compatibility between cancer cells (the seed) and the distant organ environment (the soil). For example, breast cancer often metastasizes to bones, lungs, liver, and brain, while colorectal cancer commonly spreads to the liver and lungs. Specific adhesion molecules and chemokine receptors on cancer cells interact with ligands in target organs, facilitating metastasis.
