What is adenocarcinoma? A doctor explains the lung cancer after Pope Leo's diagnosis

Lung adenocarcinoma is common and often found late. Here is what symptoms to watch for and how screening and surgery can help.

Pope Leo XIV had the lower section of his right lung removed after doctors diagnosed him with pulmonary adenocarcinoma.

While lung cancer is a leading killer, survival rates can be high if it's caught early, as the pope’s tumor appears to have been. Here are some things to know.

What is lung adenocarcinoma?

The Vatican announced the pope’s diagnosis as lung adenocarcinoma, which is one of many forms of lung cancer.

There are two main groups, small cell and non-small cell lung cancers. Among the non-small cell lung cancers, adenocarcinoma is the most common subtype and make up the vast majority of cases, according to Dr. Charu Aggarwal, an oncologist with Penn Medicine's Abramson Cancer Center.

What causes lung adenocarcinoma?

While smoking is the leading cause of lung cancer, Aggarwal noted in recent years more patients without a history of smoking are being diagnosed with lung cancer.

"We are finding that there are different biologic causes that may lead to uncontrolled cellular growth that may lead to lung cancer," Aggarwal said.

Other risks include exposure to radon gas, asbestos, radiation, secondhand smoke and air pollution, according to the American Cancer Society.

What is the survival rate for lung adenocarcinoma?

Survival rates depend greatly on the stage of the cancer when it is discovered. When diagnosed early, also known as Stage 1, the five-year survival rate is 64%, according to the National Cancer Institute. If it has spread to a different part of the body, the rate of survival declines. Stage 2 regional has a 38.2% survival rate, Stage 3 distant has a 10% survival rate and Stage 4 unknown has 5% survival rate.

Other factors such as tumor size, pathology and a person’s overall health can affect a patient's prognosis.

"Early stage lung cancer is becoming highly, highly curable," Aggarwal said. "The earlier the cancer, the more curable it is."

How is lung cancer detected?

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 — symptoms important to get checked.

"A great majority of patients with lung cancer are diagnosed when they have Stage 4 disease because they don't even become symptomatic till they have Stage four disease," Aggarwal said. "For example, till they have a cancer that metastasizes to a different organ that either causes pain or occupies part of the lung that makes it difficult to breathe."

Most cases of early stage lung cancer are discovered "accidentally," according to Aggarwal. These "incidental findings" occur when someone has an X-ray or other scan that shows a spot in a lung that needs further investigation. Doctors find these tumors before symptoms develop and possibly early enough that the cancer remains small and hasn't spread. In the pope’s case, a nodule in his lung was spotted during another exam.

The U.S. Preventive Services Task Force recommends annual screening with a low-dose CT scan, a type of X-ray, for people ages 50 to 80 who have smoked at least one pack a day for 20 years and who are either currently smoking or who may have quit within the last 15 years

But Aggarwal notes the guidelines put patients who have never smoked at a disadvantage "because we don't really have good ways to detect early lung cancers."

"I think the most important thing to remember is that a new cough that doesn't go away or shortness of breath or pain must not be overlooked in anyone and should be evaluated with a physician," she added.

How is it treated?

Surgery is a mainstay when lung cancer is detected early, and increasingly is used even in more advanced stages. 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. Each lobe has its own airway branch and dedicated blood vessels and when one is removed, “the other lobes actually pick up some of the work,” said Dr. Ben Zhang, a thoracic surgeon at Allina Health in Minneapolis.

The lungs gradually compensate over several months until most people, especially those who already were physically active, notice little to no difference with exertion, he said.

In the U.S., the average hospital stay after lung cancer surgery is two nights, Zhang said. It depends in part on how quickly the patient can get up and walk around, as well as pain and how long a tube that can drain air and fluid from the chest is needed.

Whether additional treatment is needed depends on the tumor’s stage, based on factors such as its size and whether it shows signs of spreading via the lymph nodes, and if markers on its cells suggest it may be aggressive. Additional treatment can be chemotherapy, used before surgery to shrink a tumor or afterward to attack any lingering cells. Other options include radiation, immunotherapy or what are called targeted drugs aimed at specific molecular drivers of a tumor.

Aggarwal noted that November is lung cancer awareness month and urged people to get a screening.

"Anyone with lungs can get lung cancer," she said.