How does it progress?.........2 main ways:
Direct spread...it grows from the original site, bowel, lung , breast ect and invades the tissues and impairs the function of the organ of which the cancer is invading....shortness of breath, mal absorption of bowel nutrients, blood electrolyte disturbances, kidney and liver failure and ultimately death.
Secondary spread (metastases).....spread of malignant cells into the blood stream or lymphatic system to other parts of the body....brain, lung and bones. These secondary or metastatic growths then act in the same way as the direct growths described above.
Each primary tumour has a predilection to where it likes to metastasise.
This is a very simple resumee.