Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body. Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place. Sometimes this orderly process goes wrong. New cells form when the body does not need them, and cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor.

Some important factors for cancer

• Benign tumors are not cancer
• Benign tumors are rarely life-threatening
• Generally, benign tumors can be removed, and they usually do not grow back
• Cells from benign tumors do not invade the tissues around them
• Cells from benign tumors do not spread to other parts of the body
• Malignant tumors are cancer
• Malignant tumors are generally more serious than benign tumors. They may be life-threatening
• Malignant tumors usually can be removed, but sometimes they grow back.
• Cells from malignant tumors can invade and damage nearby tissues and organs.
• Cells from malignant tumors can spread to other parts of the body. The cells spread by breaking away from the original cancer (primary tumor) and entering the bloodstream or lymphatic system. They invade other organs, forming new tumors and damaging these organs. The spread of cancer is called metastasis.

Carcinoma is another term known for Cancer that begins in the skin or in tissues that line or cover body organs. For example, carcinoma can arise in the breast, colon, liver, lung, prostate, and stomach.