Pope Leo XIV had the lower section of his right lung removed after doctors diagnosed him with the most common form of lung cancer. While lung cancer is a leading cancer killer worldwide, it is very treatable if caught early, as the pope’s tumor appears to have been. Here are some things to know.

The Vatican announced the pope’s diagnosis as lung adenocarcinoma. That’s a specific subtype of lung cancer — one of the types of so-called non-small cell lung cancer.

According to the Lung Cancer Foundation of America, adenocarcinomas can be found earlier than some other types of lung cancer because they tend to form on outer layers of the lung and to grow more slowly.

Smoking is the leading cause of lung cancer, but people who never have smoked also can get it. Other risks include exposure to radon gas, asbestos, air pollution, radiation and certain metals, according to the American Cancer Society.

Lung cancer symptoms don’t usually appear until the cancer is advanced, according to the cancer society. They can include a persistent cough, chest pain, a hoarse voice, shortness of breath, and recurrent pneumonia or bronchitis.

Sometimes, lung cancer can be found unusually early when someone has an X-ray or other imaging that shows a spot in a lung that needs further investigation. That’s called an incidental finding, leading doctors to investigate well before symptoms and possibly early enough that the cancer hasn’t yet spread. In the pope’s case, a nodule in his lung was spotted during another exam.

In the U.S., yearly screening with a low-dose CT scan, a type of X-ray, is recommended for certain people at high risk because of heavy smoking.

Surgery is the mainstay if lung cancer is detected early enough. The pope had the lower section, or lobe, of his right lung removed to try to ensure that all of the cancer was removed. The right lung has three sections or lobes while the left has two. After one lobe is removed, the rest of the lung can gradually compensate, especially in otherwise healthy and physically active people. The pope is known to engage in weekly tennis games and swimming.

Surgery is sometimes enough, but other treatments such as chemotherapy, radiation or immunotherapy can be used if there is concern about remaining or spreading cancer.

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