Why cancer comes back?
In some cases, cancer may return after treatment. This may result in the same area where it started, it is called a relapse. This may be because the tiny cancer cells that may have been left behind when the tumor was removed, or which were not destroyed by treatments such as radiation, chemotherapy, started doing more and form a tumor.
May or grown in different parts of the body, often called metastases or secondary cancer. Perhaps this is because the cancer (malignant) tumor consists of cancer cells that have the ability to spread beyond the original site. If left untreated, they can affect and destroy the surrounding tissue. Sometimes cells break away from the original (Primary) and the cancer has spread to other organs of the body, traveling in the blood or lymphatic system. When these cells reach a new area of the body they can continue to make and form a new tumor.