Talk radio icon Rush Limbaugh died Wednesday at age 70 from what his wife said were complications of lung cancer. 

When he first detailed his Stage 4 diagnosis to listeners, Limbaugh described his illness as "advanced lung cancer." Cancer starts when cells in the body begin to grow out of control, with Limbaugh’s being detected in the lungs. With lung cancers, the cells lining the bronchi and parts of the lung are typically impacted first, according to the American Cancer Society.

There are two main types of lung cancer that are diagnosed in patients including non-small cell lung cancer, which accounts for about 80-85% of cases. Non-small cell lung cancers include adenocarcinoma, squamous cell carcinoma, large cell carcinoma and other subtypes. The second main type of lung cancer is small cell lung cancer, which accounts for the remaining 10-15% of cases diagnosed. About 70% of patients diagnosed with small cell lung cancer have cancer that has already spread at the time of diagnosis.

RUSH LIMBAUGH, CONSERVATIVE TALK RADIO PIONEER, DEAD AT 70

It was not clear what type of lung cancer Limbaugh had, but in October he disclosed that his diagnosis was terminal. According to the American Cancer Society, lung cancer is by far the leading cause of cancer death among both men and women, with the average age of diagnosis being around age 70.

Limbaugh previously said one of the first indications that something was wrong was shortness of breath. Most lung cancers do not cause symptoms until they have spread, but a cough that worsens or does not go away, coughing up blood or rust-colored spit, chest pain that worsens with deep breathing, coughing or laughing, hoarseness, loss of appetite, unexplained weight loss shortness of breath, feeling tired or weak, recurring infections of pneumonia or bronchitis, and new onset of wheezing are all indications that something may be wrong, according to the American Cancer Society.

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Smoking is a leading risk factor for lung cancer, with about 80% of lung cancer deaths thought result from the addiction. Exposure to secondhand smoke, exposure to radon, exposure to asbestos and other cancer-causing agents as well as certain dietary supplements and arsenic in water are all listed as risk factors for the illness. Previous exposure to radiation therapy, air pollution and family history are also potential risk factors.

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It is usually diagnosed through imaging and blood tests, with staging usually determined by size and spread. Treatment depends on cancer type and spread, but could include surgery, radiation, chemotherapy, immunotherapy, and targeted drug therapy.

Limbaugh’s wife did not reveal what kind of complications he died from, only that it was somehow related to his diagnosis.

"Every day remains a gift," Limbaugh had told his listeners in December. "You know, I wake up every morning, and I thank God that I did."