Cancer is not a single disease - it is a large, complex family of diseases that can affect virtually every part of the body. Physicians diagnose more than 1/3 million cases of cancer every year - with half of those cases occurring in the lung, prostate, breast, colon, and rectum. Cancer is second only to heart disease as the leading cause of death in the U.S. and, although it can strike at any age, cancer is more common in people 50 or older.
Cancer begins in the body's cells, which constantly divide and multiply to replace old, damaged cells. Sometimes, cells begin to divide unnecessarily, forming excess tissue known as a tumor. In many cases, these tumors are not cancerous - they are benign. While benign tumors may cause health problems depending on their size and location, they are generally not life-threatening. If, however, abnormal cells begin to divide, they may for a malignant, or cancerous tumor.
Most malignant tumors grow rapidly, invading nearby organs and tissues - a process referred to as metastasis. Cancerous cells can also travel through the bloodstream to other regions of the body.
There are many different types of cancer. Several factors, including the location of the cancer cells and their appearance under the microscope, help determine the specific cancer diagnosis.
The vast majority of cancers - as many as 80% - are considered sporadic, or without a clear genetic predisposition.
Despite popular belief, many cancers don't display obvious symptoms or cause pain until well advanced.
Today, physicians have access to a broad range of methods for diagnosing cancer. As researchers learn more about the way cancer develops and spreads, they develop new diagnostic tools and refine existing methods.
Cancer treatments fall into four major categories: surgery, radiation therapy, chemotherapy, Cause and immunotherapy.