Cancer

Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. 

Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and multiply (through a process called cell division) to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.

Sometimes this orderly process breaks down, and abnormal or damaged cells grow and multiply when they shouldn’t. These cells may form tumors, which are lumps of tissue. Tumors can be cancerous or not cancerous (benign). 

Cancerous tumors spread into, or invade, nearby tissues and can travel to distant places in the body to form new tumors (a process called metastasis). Cancerous tumors may also be called malignant tumors. Many cancers form solid tumors, but cancers of the blood, such as leukemias, generally do not.

Benign tumors do not spread into, or invade, nearby tissues. When removed, benign tumors usually don’t grow back, whereas cancerous tumors sometimes do. Benign tumors can sometimes be quite large, however. Some can cause serious symptoms or be life threatening, such as benign tumors in the brain.

Cancer is the second-leading cause of death in the world. But survival rates are improving for many types of cancer, thanks to improvements in cancer screening, treatment and prevention.

There are many types of cancer. Cancer can develop anywhere in the body and is named for the part of the body where it started. For instance, breast cancer that starts in the breast is still called breast cancer even if it spreads (metastasizes) to other parts of the body.

There are two main categories of cancer:

• Hematologic (blood) cancers are cancers of the blood cells, including leukemia, lymphoma, and multiple myeloma.
• Solid tumor cancers are cancers of any of the other body organs or tissues. The most common solid tumors are breast, prostate, lung, and colorectal cancers.

Symptoms

Signs and symptoms caused by cancer will vary depending on what part of the body is affected. Some general signs and symptoms associated with, but not specific to, cancer, include:

• Fatigue
• Lump or area of thickening that can be felt under the skin
• Weight changes, including unintended loss or gain
• Skin changes, such as yellowing, darkening or redness of the skin, sores that won't heal, or changes to existing moles
• Changes in bowel or bladder habits
• Persistent cough or trouble breathing
• Difficulty swallowing
• Hoarseness
• Persistent indigestion or discomfort after eating
• Persistent, unexplained muscle or joint pain
• Persistent, unexplained fevers or night sweats
• Unexplained bleeding or bruising