How can cancer spread from its original site to other parts of the body?

Cancer spreads from its original site through a complex process known as metastasis. This progression typically involves several critical stages:

• Invasion: Cancer cells detach from the primary tumor by losing their ability to adhere to neighboring cells and the extracellular matrix. To move through tissues, they secrete enzymes that digest the matrix and breach the basement membrane, creating a path to reach nearby blood vessels or lymphatic channels.123
• Dissemination: Once inside the circulatory or lymphatic system, cancer cells are transported throughout the body. While many are destroyed, some survive and lodge in the capillaries of distant organs.41
• Colonization: Cells exit the vessels and establish secondary tumors. This spread is often influenced by the circulatory system's architecture—leading to "downstream" growth—or by "homing" mechanisms, where cancer cells are attracted to specific tissues through molecular affinities, such as the interaction between receptor proteins on cancer cells and molecules in the target tissue.412

The ability to metastasize is a hallmark of malignant disease and is the primary reason cancer is often fatal.12