|
|
Normal cells grow, divide, and die in an orderly fashion. This keeps certain cells from invading other cells. Cancer occurs when the DNA of those cells becomes damaged or mutated and their limits are removed, allowing them to reproduce uncontrollably. These abnormal cells usually form a lump that is known as a tumor. In a benign tumor the abnormal cells do not spread into surrounding areas, but malignant tumors do have the ability to spread. If the tumor is left untreated then it may spread and destroy the neighboring tissue. Sometimes cancer cells can even break off the original tumor and spread to other organs and tissue through the bloodstream or the lymphatic system. The lymphatic system is part of the immune system. It is a complex system that includes the bone marrow, the thymus and the spleen, and lymph nodes throughout the body that are connected by a network of lymphatic vessels. When the cancer cells reach a new site they may continue to divide and form a new tumor, which is referred to as a secondary tumor or a metastasis.
