Lung cancer is the most commonly diagnosed cancer worldwide and the leading cause of cancer death, responsible for nearly 2.5 million new cases in 2022, or about one in eight cancer diagnoses globally. The World Health Organization (WHO) plays a central role in classifying lung tumors, tracking global burden, and shaping prevention strategies. Here’s what the latest WHO data and classifications tell us about the disease.
Lung Cancer by the Numbers
In 2022, lung cancer accounted for 12.4% of all new cancer cases worldwide, making it the single most frequently diagnosed cancer. It was followed by female breast cancer (11.6%), colorectal cancer (9.6%), prostate cancer (7.3%), and stomach cancer (4.9%). The death toll is even more disproportionate: an estimated 1.8 million people died from lung cancer that year, representing 18.7% of all cancer deaths. No other cancer comes close. Colorectal cancer, the second-leading cause of cancer death, accounted for 9.3%.
The burden falls especially hard on men. Lung cancer is the leading cause of cancer death among men in 89 countries. Among women, it ranks alongside breast cancer as one of the two most common cancers in terms of both new cases and deaths.
How the WHO Classifies Lung Tumors
The WHO Classification of Lung Tumors serves as the international standard pathologists use to identify and categorize lung cancers. The most recent edition, published in 2021, introduced several important updates from the previous 2015 version.
Lung cancer falls into a few major categories. Adenocarcinoma, which forms in the cells lining the airways, is the most common type. Squamous cell carcinoma develops in the flat cells lining the bronchi. Small cell carcinoma, grouped under neuroendocrine tumors, is an aggressive form that grows and spreads quickly. The 2021 classification also added a rare entity called thoracic SMARCA4-deficient undifferentiated tumor and recognized a new benign growth called bronchiolar adenoma.
One of the biggest shifts in the 2021 edition is a stronger emphasis on genetic testing. Pathologists are now encouraged to look at not just what tumor cells look like under a microscope, but what genetic mutations drive them. For adenocarcinoma specifically, the classification recommends documenting the percentage of different growth patterns within the tumor, which feeds into a formal grading system that helps predict how aggressive the cancer is likely to be. Another new addition is the recognition that cancer cells spreading through tiny air spaces in the lung tissue carries prognostic significance, meaning it can affect the outlook for a patient.
The Role of Biomarker Testing
Five genetic biomarkers are now considered clinically actionable in lung cancer: ALK, BRAF, EGFR, ROS1, and PD-L1. Testing for these markers helps determine whether a patient’s cancer can be targeted with specific therapies rather than standard chemotherapy. Despite this, adoption has been slow. Between 2018 and 2020, only 46% of patients with advanced non-small cell lung cancer had all five of these biomarkers tested at community oncology practices in the United States. Part of the problem is that the WHO classification still lists genetic testing as a “desirable” criterion for adenocarcinoma rather than an essential one. Advocates argue that making biomarker names part of the official WHO diagnosis would push pathologists to test for them routinely as part of the initial workup.
What Causes Lung Cancer
Smoking remains the dominant risk factor, responsible for roughly 85% of all lung cancer cases. But that leaves a substantial 15% of cases occurring in people who have never smoked or who have other primary exposures. The WHO identifies several additional risk factors: secondhand smoke, workplace exposure to asbestos, radon, and certain industrial chemicals, outdoor air pollution, inherited cancer syndromes, and chronic lung diseases like COPD.
Air pollution deserves particular attention. It is the second leading cause of premature death globally and is estimated to cause around 14% of lung cancers. Fine particulate matter (PM2.5), the tiny particles produced by vehicle exhaust, industrial activity, and wildfires, is especially dangerous. Recent research has clarified how these particles trigger cancer, particularly in cells that already carry certain genetic mutations. This helps explain why some people who have never smoked still develop lung cancer after prolonged exposure to polluted air.
Screening for Early Detection
Lung cancer is often diagnosed late because it rarely causes symptoms in its early stages. The only recommended screening test is a low-dose CT scan, a quick imaging procedure that uses less radiation than a standard CT. Screening is not recommended for the general population. It is targeted at high-risk adults based on their smoking history and age.
The U.S. Preventive Services Task Force recommends yearly screening for people who meet all three criteria: a smoking history of 20 pack-years or more (one pack per day for 20 years, or equivalent), current smokers or those who quit within the past 15 years, and age 50 to 80. Screening stops when a person turns 81, has been smoke-free for 15 years or more, or develops a condition that would make lung surgery impractical. These criteria aim to balance the benefits of catching cancer early against the risks of false positives and unnecessary procedures.
Tobacco Control and Prevention
The WHO’s primary strategy for reducing lung cancer globally centers on tobacco control through a framework called MPOWER. This set of six policy measures includes monitoring tobacco use, protecting people from secondhand smoke, offering help to quit, warning about tobacco’s dangers, enforcing bans on advertising, and raising taxes on tobacco products.
Of all these measures, raising tobacco taxes has consistently proven the most effective at reducing smoking rates at the population level. Research modeling the impact of full MPOWER implementation across 30 European countries found that between 9.9% and 33% of lung cancer cases could be prevented over a 20-year period, depending on the country. In Saudi Arabia, where MPOWER measures were introduced in 2012 at varying intensity levels, smoking prevalence showed a small but consistent annual decline in the years that followed. Full implementation of the highest-level measures could cut smoking rates in half, potentially preventing thousands of lung cancer cases.
These prevention strategies matter because treatment for advanced lung cancer, while improving, still carries a poor prognosis compared to cancers caught early or prevented altogether. Reducing the global smoking rate remains the single most impactful lever for lowering lung cancer deaths worldwide.