The four types of lung cancer are defined by where the cancer cells start

Lung cancer is sorted into types based on which cells in the lung become cancerous. The two broadest categories are small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Within non-small cell lung cancer, there are three main subtypes: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. The type matters because it affects how fast the cancer grows, where it spreads, and which treatments are most likely to work.

About 85 percent of lung cancers are non-small cell. Small cell lung cancer accounts for most of the remainder. The distinction between them is visible under a microscope — the cancer cells in small cell lung cancer are smaller and more tightly packed — but the real difference is in behavior. Small cell lung cancer grows faster and spreads earlier, while non-small cell types tend to grow more slowly.

Key Takeaways

  • Small cell lung cancer grows quickly and spreads to other parts of the body early, making it harder to treat but sometimes more responsive to chemotherapy.
  • Adenocarcinoma, the most common type of non-small cell lung cancer, often starts in the outer edges of the lungs and is the type most often seen in people who have never smoked.
  • Squamous cell carcinoma typically begins in the central airways of the lungs and is most common in people with a history of smoking.
  • Large cell carcinoma is the rarest type and tends to grow and spread quickly, similar to small cell lung cancer in its behavior.
  • Knowing your lung cancer type helps doctors choose the most effective treatment and predict how the cancer is likely to behave.

Small cell lung cancer: fast-growing and early-spreading

Small cell lung cancer (SCLC) accounts for about 10 to 15 percent of all lung cancers. It grows quickly and spreads to other organs — usually the brain, liver, and bones — earlier than other types. Because it spreads so early, most people with SCLC are diagnosed at an advanced stage.

The tradeoff is that small cell lung cancer often responds well to chemotherapy and radiation, at least initially. However, it tends to develop resistance to treatment over time. SCLC is almost always linked to smoking; it is rare in people who have never smoked. Doctors typically divide SCLC into two stages: limited stage (cancer confined to one lung and nearby lymph nodes) and extensive stage (cancer that has spread beyond the lung).

Adenocarcinoma: the most common type overall

Adenocarcinoma is a non-small cell lung cancer that starts in the mucus-producing glands lining the airways. It is the most common type of lung cancer overall, accounting for about 40 percent of all cases. Unlike small cell lung cancer, adenocarcinoma can develop in people who have never smoked, though smoking increases the risk.

Adenocarcinoma typically grows in the outer edges of the lungs, away from the central airways. This location means it may not cause symptoms until the cancer is fairly advanced. When adenocarcinoma is caught early — sometimes by accident on a CT scan done for another reason — the outlook is often better than for other types. Adenocarcinoma can be further divided into subtypes based on how the cells look under the microscope, and these subtypes can affect treatment choices.

Squamous cell carcinoma: linked to smoking and central location

Squamous cell carcinoma is a non-small cell lung cancer that starts in the flat cells lining the airways in the center of the lungs. It accounts for about 25 to 30 percent of lung cancers and is strongly associated with smoking. It is uncommon in people who have never smoked.

Because squamous cell carcinoma develops in the central airways, it may cause symptoms earlier than adenocarcinoma — coughing up blood or a persistent cough that changes character. This central location can make it easier to see on imaging and sometimes easier to biopsy. Squamous cell carcinoma tends to grow more slowly than small cell lung cancer but faster than some adenocarcinomas, though there is variation from person to person.

Large cell carcinoma: rare and aggressive

Large cell carcinoma is the rarest type of lung cancer, accounting for only 10 to 15 percent of non-small cell cases. It is called "large cell" because the cancer cells are noticeably larger than those in small cell lung cancer, but it does not fit neatly into the adenocarcinoma or squamous cell categories.

Large cell carcinoma tends to grow and spread quickly, similar to small cell lung cancer in its behavior. It can start anywhere in the lung. Because it is rare, there is less research on the best way to treat it, and doctors often use the same approaches used for other non-small cell lung cancers. The outlook for large cell carcinoma is generally less favorable than for adenocarcinoma or squamous cell carcinoma.

How doctors determine which type you have

To identify the type of lung cancer, a doctor must obtain a tissue sample. This can happen through a biopsy — a procedure where a needle or scope is used to collect cells from the lung — or sometimes from fluid around the lungs or from sputum (coughed-up material). The sample is then examined under a microscope by a pathologist, who identifies which type of cells are cancerous.

In some cases, genetic testing is also done on the cancer cells. This testing looks for specific mutations that may make certain treatments more effective. For example, some adenocarcinomas have mutations in genes like EGFR or ALK, and knowing about these mutations can change which drugs are recommended. This is why the type of lung cancer and the genetic makeup of the cancer cells both matter for treatment planning.

Why the type affects your treatment options

Different lung cancer types respond differently to chemotherapy, radiation, targeted drugs, and immunotherapy. Small cell lung cancer is typically treated with chemotherapy and radiation, sometimes combined. Non-small cell lung cancers may be treated with surgery (if caught early), chemotherapy, targeted therapy (drugs that attack specific mutations), immunotherapy, or a combination of these.

Adenocarcinoma is more likely to have targetable mutations, which means some people can take a pill that attacks their specific cancer rather than undergoing chemotherapy. Squamous cell carcinoma is less likely to have these mutations but may respond well to immunotherapy. Large cell carcinoma is treated similarly to other non-small cell types, though outcomes tend to be less favorable. Knowing your type helps your doctor narrow down which treatments are most likely to work for your specific cancer.

Frequently Asked Questions

Can you have more than one type of lung cancer at the same time?

It is possible but uncommon. Most people have one type of lung cancer. If a person has had lung cancer before and develops a new cancer in the lung years later, it may be a different type or a recurrence of the original type. Your doctor can determine this through biopsy and genetic testing.

Does the type of lung cancer depend on smoking history?

Smoking history influences which types are more likely. Small cell and squamous cell carcinomas are strongly linked to smoking. Adenocarcinoma can occur in people who have never smoked, though smokers can also develop it. Large cell carcinoma can occur in smokers and non-smokers. Smoking increases the overall risk of all types.

Is one type of lung cancer more curable than the others?

Adenocarcinoma, especially when caught early, often has a better outlook than other types. Small cell lung cancer, despite responding well initially to treatment, tends to recur. Squamous cell carcinoma outcomes vary. Large cell carcinoma generally has a less favorable outlook. However, individual outcomes depend on the stage at diagnosis, the person's overall health, and how the specific cancer responds to treatment.

Can the type of lung cancer change over time?

The original type does not change, but cancer can evolve genetically. New mutations may develop as the cancer grows, which is why repeat biopsies are sometimes done if treatment stops working. This helps doctors understand what has changed and whether a different treatment might work better.