Cancer occurs when cells in a part of the body begin to grow out of control. They continue to grow and crowd out normal cells. Although there are many kinds of cancer, they all have in common this out-of-control growth of cells.Different kinds of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That’s why people with cancer need treatment that is aimed at their kind of cancer.
Sometimes cancer cells break away from a tumor and spread to other parts of the body through the blood or lymph system. They can settle in new places and form new tumors. When this happens, it is called metastasis Cancer that has spread in this way is called metastatic cancer.Even when cancer has spread to a new place in the body, it is still named after the part of the body where it started. For example, if prostate cancer spreads to the bones, it is still called prostate cancer. If breast cancer spreads to the lungs, it is still breast cancer. When cancer comes back in a person who appeared to be free of the disease after treatment, it is called a recurrence.
Sometimes, however, cells become abnormal and keep dividing to form more cells without control or order, creating a mass of excess tissue called a tumor. Tumors can be malignant (cancerous) or benign (not cancerous).The cells in malignant tumors can invade and damage nearby tissue and organs. Cancer cells can also break away from a malignant tumor and travel through the bloodstream or lymphatic system to form new tumors in other parts of the body.
Types The main types of cancer are sarcoma, carcinoma, lymphoma and myeloma, leukemia, central nervous system cancers.