Some cancers and cancer treatments can change the number of blood cells circulating in the blood. Also, cancers can spread by shedding cells into the bloodstream that may then settle in another part of the body.
The lymphatic system normally helps to trap and destroy cancer cells as well as bacteria and other harmful organisms.Sometimes cancer cells get trapped in lymph nodes close to the cancer and may then start to grow there.
The hormone system is a network of glands and organs in the body that produce hormones. Cancer and its treatments can sometimes change hormone levels and cause side effects. But some treatments can help to control cancer or prevent it coming back by changing particular hormone levels.