What is lung adenocarcinoma, the cancer diagnosed in Pope Leo?

VATICAN CITY: Pope Leo was diagnosed with lung adenocarcinoma after doctors removed the lower lobe of his right lung during surgery on Tuesday, the Vatican said. Here are some facts about the disease. What is it? Adenocarcinoma is a type of cancer that forms in glandular cells, which produce substances such as mucus. In the lungs, it develops in cells lining the air sacs and is the most common subtype of non-small cell lung cancer (NSCLC), the category that accounts for about 80%-85% of lung cancers. Adenocarcinoma represents roughly 40% of all lung cancer cases, according to the Lung Cancer Foundation of America. It is typically found in the outer parts of the lungs and tends to grow more slowly than some other forms of lung cancer, increasing the chances of detection before it has spread. Who gets it? Smoking remains the main risk factor. However, adenocarcinoma is also the most common type of lung cancer among people who have never smoked. The pope is not known to have been a smoker. Symptoms Early-stage disease often causes no symptoms and may be discovered during scans performed for other reasons. As the cancer progresses, symptoms can include a persistent cough, shortness of breath or wheezing, coughing up blood, chest, shoulder or back pain, unexplained weight loss and fatigue. The Vatican has said the tumour was found during a routine health check. Leo said on Sunday that the growth was "well-contained" and had been spotted early. How is it treated? For patients whose cancer is confined to the lung, surgery offers the best chance of a cure. The standard operation is a lobectomy, as occurred on Tuesday, in which an entire lobe of the lung is removed. Doctors consider it the preferred treatment when the tumour is limited to a single lobe because it maximises the chances of removing all cancerous tissue while preserving as much lung function as possible. Depending on the stage of the disease, treatment can also include chemotherapy, radiotherapy, targeted drugs and immunotherapy. The Vatican has not given any information yet on what follow-up treatment the pope might need. Prognosis Doctors say prognosis depends heavily on the stage of the cancer and whether it has spread beyond the lung. The Vatican has not disclosed the size of the tumour or whether lymph nodes were affected, making it impossible to assess Leo's individual prognosis at this stage. According to the American Cancer Society, the five-year relative survival rate for non-small cell lung cancer is 67% when the disease remains confined to the lung. The rate falls to about 40% when the disease has spread to nearby tissues or lymph nodes and to about 12% when it has spread to distant organs. However, it says people being diagnosed now may have a better outlook than these statistics suggest because of improving treatments. Medical experts also caution that outcomes vary widely depending on tumour size, lymph node involvement, a patient's age and overall health. (Sources: This factbox drew on information posted online by the Lung Cancer Foundation of America, the National Library of Medicine and the American Cancer Society.)