The five most common types of lung cancer are adenocarcinoma, squamous cell carcinoma, large cell carcinoma, small cell carcinoma, and carcinoid tumors. The first three fall under the umbrella of non-small cell lung cancer (NSCLC), which accounts for roughly 77% of all cases. Small cell lung cancer makes up about 12%, and carcinoid tumors are the rarest of the five.
Adenocarcinoma
Adenocarcinoma is the most common type of lung cancer by a wide margin, representing about 45% of all cases in the United States. It develops in the cells that line the tiny air sacs deep in the lungs, the same cells responsible for producing mucus and other substances. Because it tends to grow in the outer regions of the lung, adenocarcinoma sometimes reaches a noticeable size before causing symptoms like coughing or chest pain.
This is also the type most frequently diagnosed in people who have never smoked. Between 50% and 60% of lung cancers in nonsmokers are adenocarcinomas. Globally, adenocarcinoma rates have been rising, with research from the International Agency for Research on Cancer linking some of that increase to air pollution exposure. Women are disproportionately affected: nearly 60% of all female lung cancers worldwide are adenocarcinomas, compared to about 46% in men.
Adenocarcinoma is also the subtype where genetic testing matters most for treatment decisions. Tumors are routinely tested for specific mutations in genes like EGFR, ALK, KRAS, and BRAF. When one of these mutations is present, targeted therapies can block the specific signals driving tumor growth, often with fewer side effects than traditional chemotherapy.
Squamous Cell Carcinoma
Squamous cell carcinoma accounts for about 21% of lung cancers. It starts in the flat, thin cells that line the inside of the airways and tends to develop in the central part of the lungs, near the main bronchi. This central location means it can block airways relatively early, leading to symptoms like persistent cough, coughing up blood, or recurring lung infections.
This type has a stronger link to smoking than adenocarcinoma does. Among people who have never smoked, only 10% to 20% of lung cancers are squamous cell. Globally, it’s the second most common subtype, with about 461,000 new cases in men and 156,000 in women diagnosed worldwide in 2022.
Large Cell Carcinoma
Large cell carcinoma makes up roughly 6.5% of lung cancers worldwide. The name comes from the appearance of the cancer cells under a microscope: they’re noticeably large and lack the specific features that would classify them as adenocarcinoma or squamous cell. In practice, “large cell” often functions as a catch-all diagnosis for non-small cell tumors that don’t fit neatly into the other categories.
Large cell carcinoma can appear anywhere in the lung and tends to grow and spread faster than adenocarcinoma or squamous cell carcinoma. Because its cells are less differentiated (meaning they look more abnormal and less like normal lung tissue), it can be harder to characterize and may require additional molecular testing to guide treatment.
Small Cell Lung Cancer
Small cell lung cancer is biologically distinct from the three types above. It grows and spreads quickly, often reaching other parts of the body before it’s diagnosed. This aggressive behavior is the reason it’s classified separately from NSCLC and staged differently, using just two categories instead of the more detailed staging system used for other lung cancers.
Limited-stage means the cancer is still confined to one lung and possibly nearby lymph nodes. Extensive-stage means it has spread beyond that, to the other lung or to distant organs. Most people are diagnosed at the extensive stage because the cancer moves so fast. The five-year survival rate for all stages combined is about 9%, compared to 32% for non-small cell lung cancer overall. When caught early and still localized, the five-year survival rate for small cell is 34%, but that’s uncommon.
Smoking is the dominant risk factor. Only 6% to 8% of lung cancers in nonsmokers are small cell. Other risk factors include exposure to radon, asbestos, and other workplace carcinogens, as well as a family history of lung cancer.
Carcinoid Tumors
Lung carcinoid tumors are the least common of the five types and behave very differently from the others. They originate in neuroendocrine cells, specialized cells in the lungs that help regulate airflow and blood flow. Carcinoid tumors are divided into two subtypes: typical and atypical.
Typical carcinoid tumors grow slowly and rarely spread to other organs. They make up the majority of lung carcinoid diagnoses and generally carry a favorable prognosis. Atypical carcinoid tumors grow faster and are more likely to metastasize, though they’re still considerably less aggressive than small cell lung cancer (which also has neuroendocrine features but behaves far more aggressively).
Because carcinoid tumors are slow-growing, they may not cause symptoms for years. When symptoms do appear, they can include wheezing, recurrent pneumonia, or coughing up blood, depending on where the tumor sits in the airway.
How Survival Rates Compare
Prognosis varies enormously depending on both the type of lung cancer and how early it’s caught. For non-small cell lung cancer (which includes adenocarcinoma, squamous cell, and large cell), the five-year survival rate is 67% when the cancer is still localized, 40% when it has spread to nearby lymph nodes, and 12% when it has reached distant organs.
Small cell lung cancer has lower survival rates across every stage: 34% for localized disease, 20% for regional spread, and 4% for distant metastasis. Carcinoid tumors, particularly the typical subtype, carry significantly better survival rates than any of the others, though exact figures depend on the specific subtype and stage.
These numbers are based on people diagnosed between 2012 and 2021, and treatments have continued to improve since then, particularly for adenocarcinoma with targetable genetic mutations and for cancers that respond to immunotherapy.
Why Subtype Matters for Treatment
Knowing which of the five types you’re dealing with shapes nearly every treatment decision. Adenocarcinomas with specific gene mutations can be treated with targeted drugs that block those mutations directly. Squamous cell carcinomas, which carry different molecular profiles, respond to different drug combinations. Small cell lung cancer is typically treated with chemotherapy, sometimes combined with radiation, because it responds initially but tends to recur. Carcinoid tumors are often treated with surgery alone if caught before spreading.
This is why pathology reports for lung cancer go well beyond simply confirming “lung cancer.” The tissue sample is examined under a microscope to determine the cell type and then tested for molecular markers that further refine the diagnosis. Two people with lung adenocarcinoma may receive completely different treatments depending on which genetic mutations their tumors carry.