Cancer is a disease that results when abnormal cells in the body grow out of control. Normal cells perform a specific function.
Cells that are old or that have been damaged die and are replaced by new, healthy cells. Cancer cells are abnormal cells that are typically caused by genetic mutation.
Cancer cells display three disease-causing characteristics.
• Uncontrolled growth - cancer cells reproduce and divide at an abnormal rate
• Invasion - cancer cells damage or destroy the surrounding tissue
– cancer cells sometimes spread to other parts of the body and create new tumors in other locations.
Some types of cancer cells form clusters known as tumors. These tumors display the disease causing properties of uncontrolled growth, invasion, and metastasis. Cancerous tumors are called malignant tumors because they cause disease and possible death.
Non-cancerous cells can also form into tumors. They are known as benign tumors because they do not display disease-causing characteristics.
Cancer is named based on the function of the abnormal cells or the body part or organ where the cells originated. For example, cancer that begins in the liver is called liver cancer. Cancer that begins in the cells of the lung is called lung cancer.
Cancer cells that metastasize or travel to other parts of the body are still named after the kind of cell that makes up the cancer. For example, prostate cancer that metastasizes to the lung is still called prostate cancer.
Cancer cells are grouped into larger categories including:
• Carcinoma – cancer in the skin or the surface of internal organs
• Sarcoma – cancer in supportive tissue including bone, cartilage, muscle, and blood vessels
• Leukemia – cancer in bone marrow and other tissue that produces blood
• Lymphoma and myeloma – cancer in the immune system cells
• Central nervous system – cancer in the brain and spinal cord
There are more than 100 types of cancer.