Oncology

Oncology-Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.

Causes, incidence, and risk factors

Cells are the building blocks of living things. Cancer grows out of normal cells in the body. Normal cells multiply when the body needs them and die when the body doesn't need them. Cancer appears to occur when the growth of cells in the body is out of control and cells divide too quickly. It can also occur when cells forget how to die. There are many different kinds of cancers. Cancer can develop in almost any organ or tissue, such as the lung, colon, breast, skin, bones, or nerve tissue. There are many causes of cancers, including:

Benzene and other chemicals
Drinking excess alcohol
Environmental toxins, such as certain poisonous mushrooms and a type of poison that can grow on peanut plants (aflatoxins)
Excessive sunlight exposure
Genetic problems
Obesity
Radiation
Viruses

However, the cause of many cancers remains unknown.

The most common cause of cancer-related death is lung cancer.

The three most common cancers in men in the United States are:

In women in the United States, the three most common cancers are:

Breast cancer
Colon cancer
Lung cancer

Some cancers are more common in certain parts of the world. For example, in Japan, there are many cases of stomach cancer but in the United States this type of cancer is rare. Differences in diet can play a role. Some other types of cancers include:

Symptoms

Symptoms of cancer depend on the type and location of the cancer. 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 pancreatic cancer, symptoms often do not start until the disease has reached an advanced stage.