Рак является одной из вредных болезней

                                                Cancer is a harmful disease.

Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells. Cancer known medically as a malignant neoplasm, is a broad group of various diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream.

Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.

Symptoms of cancer depend on the type and location of the tumor. For example, lung cancer can cause coughing, shortness of breath, or chest pain. Colon cancer often causes diarrhea, constipation, and blood in the stool. Some cancers may not have any symptoms at all. In certain cancers, such as gallbladder cancer, symptoms often do not start until the disease has reached an advanced stage.

The following symptoms can occur with most cancers:

       - Chills

       - Fatigue

       - Fever

       - Loss of appetite

       - Malaise

       - Night sweats

       - Weight loss

In 2008 approximately 12.7 million cancers were diagnosed (excluding non-melanoma skin cancers and other non-invasive cancers) and 7.6 million people died of cancer worldwide. Cancers as a group account for approximately 13% of all deaths each year with the most common being: lung cancer (1.4 million deaths), stomach cancer (740,000 deaths), liver cancer (700,000 deaths), colorectal cancer (610,000 deaths), and breast cancer (460,000 deaths).[93] This makes invasive cancer the leading cause of death in the developed world and the second leading cause of death in the developing world. Over half of cases occur in the developing world.

Global cancer rates have been increasing primarily due to an aging population and lifestyle changes in the developing world. The most significant risk factor for developing cancer is old age. Although it is possible for cancer to strike at any age, most people who are diagnosed with invasive cancer are over the age of 65. According to cancer researcher Robert A. Weinberg, "If we lived long enough, sooner or later we all would get cancer. Some of the association between aging and cancer is attributed to immunosenescence, errors accumulated in DNA over a lifetime, and age-related changes in the endocrine system.

The three most common childhood cancers are leukemia (34%), brain tumors (23%), and lymphomas (12%). Rates of childhood cancer have increased by 0.6% per year between 1975 to 2002 in the United States and by 1.1% per year between 1978 and 1997 in Europe.

One of the best ways to prevent cancer is to not smoke or chew tobacco. Many cancers can be prevented by avoiding risk factors such as excessive exposure to sunlight and heavy drinking. Cancer screenings, such as mammography and breast examination for breast cancer and colonoscopy for colon cancer, may help catch these cancers at their early stages when they are most treatable. Some people at high risk for developing certain cancers can take medication to reduce their risk.