The Most Common Types of Lung Cancer

It's easy to think that lung cancer is one diagnosis with one possible outcome. The truth is that there are several types of lung cancer with key differences in what causes them. There are also differences in how each type of lung cancer develops in the body and how it is treated.

Most lung cancer diagnoses fall into a few types and subtypes. However, all people with lung cancer have unique experiences, even if they have the same disease.

This article will help you learn more about these types of lung cancer and how they might vary based on age, sex, smoking status, and other factors.

Main Types of Lung Cancer

Primary lung cancers are those that start in the lungs rather than spreading (metastasizing) to the lungs from somewhere else in the body.

There are two main types of primary lung cancers:

• Non-small cell lung cancer (NSCLC) is the most common type of lung cancer overall. It accounts for 80% to 85% of lung cancers in the United States.
• Small cell lung cancers (SCLC) are diagnosed in 10% to 15% of lung cancer cases.

A third type, called a carcinoid tumor, is less common in the lungs. It accounts for just 1% to 2% of lung cancers.

NSCLC and SCLC are also broken down into specific subtypes. The names are based on the kinds of cells that make up the tumors when they're seen under a microscope.

Non-Small Cell Lung Cancer

NSCLC typically grows and spreads more slowly than SCLC. Both are linked with smoking, but NSCLC is also the most common type of lung cancer in younger people and in people who have never smoked.

The risks and causes may depend on what subtype of NSCLC is diagnosed. There are three main subtypes:

• Lung adenocarcinoma accounts for 40% to 50% percent of NSCLC cases.
• Squamous cell carcinoma occurs in some 20% to 30% of all NSCLC cases.
• Large cell lung cancer is responsible in about 3% to 10% of all NSCLC cases.
  

Small Cell Lung Cancer

SCLC is typically an aggressive, fast-growing cancer.

It is strongly linked with smoking, although other factors including radon exposure may be involved. (Radon is an odorless, colorless gas that seeps into homes from the soil around it.)

Two subtypes of SCLC are:

• Small cell carcinoma
• Combined small cell carcinoma (cells mixed with another type)
  

Differences Based on Sex

Men continue to have higher incidence rates of lung cancer than women; however, the gap is closing largely due to health policy changes and smoking cessation.

NSCLC is a common lung cancer diagnosis in both men and women, with the adenocarcinoma subtype being the most prevalent. However, researchers describe lung adenocarcinomas as "a different disease in women and men."

Among women, lung adenocarcinomas account for 40% to 60% of their lung cancer cases. Roughly half of these cancers in women are related to smoking, compared to 85% of the cases in men who are smokers. Women also tend to be younger at diagnosis and respond differently to treatments.

Men with NSCLC are more likely to develop squamous cell lung cancer, which is linked with smoking. However, they are less likely to be diagnosed with SCLC than women.

Differences Based on Age

Lung cancer, as with many diseases, is generally more common in older people, with the average age of diagnosis being 70. Only 5% of all cancers are diagnosed in young adults ages 18-39.

Lung adenocarcinoma is the most common type of lung cancer in young adults, accounting for nearly 50% of cases. Carcinoid lung tumors tend to be found most frequently in people aged 45-55, but can be diagnosed at any age, including in children and adolescents. On the other hand, SCLC is relatively rare in young people, seen in less than 5% of lung cancer cases.

Young adults with lung cancer are much more likely to have a genetic factor that contributes to their lung cancer. For this reason, they may have genetic changes that may be treated with newer therapies that target specific mutations.

Smokers vs. Non-Smokers

In many ways, lung cancer in non-smokers is quite different from lung cancer in people who smoke. This applies to even the most common types of the disease.

Both NSCLC and SCLC are linked with a history of smoking, though SCLC's association is much stronger.

Of the three NSCLC subtypes, lung adenocarcinoma is the one most likely to be found in people who never smoked (50% to 60%). Around 10% to 20% of people who never smoked are diagnosed with squamous cell carcinoma. Only 6% to 8% of people who never smoked are diagnosed with SCLC.

Carcinoid tumors do not appear to be associated with smoking. They are found in smokers and non-smokers in numbers that are similar to those seen in the general population.

Rates and the Role of Genetics

Lung cancer rates have shifted over time. That's partly because people began to quit or avoid smoking because of the health impacts.

One of the biggest questions, though, is why lung cancer rates have climbed in younger people and those who have never smoked.

Environmental factors like air pollution may be part of the reason, but that doesn't explain many of the cases. Research led by the National Cancer Institute and National Institutes of Health points to genetics.

Their September 2021 study looked at changes in the genes of 232 people with NSCLC diagnoses who never smoked, comparing their normal tissue with tumor samples.

Of the study group, 189 had lung adenocarcinomas while the rest were other types. The study found that gene mutations from natural processes inside the body were associated with the lung cancers.

The researchers also reported three new genetic subtypes of lung cancer in these never-smokers.

While they caution that more research is needed, the findings point to the possibility of future treatment targets.

Targetable Mutations in Lung Cancer

Science continues to delve deeper into the genetic links to lung and other cancers. Still, many healthcare providers and cancer specialists (oncologists) recommend genetic testing for people with cancer.

That's especially true for people with NSCLC lung cancer. Targeted therapies are available or in development for people with specific cancer-related changes (mutations) in genes, including:

• EGFR
• ROS1
• ALK
• BRAF

Tumors that have treatable mutations are more commonly found in young adults, never-smokers, and women. However, many other people with lung cancer may benefit from targeted therapies as well.

Summary

There are several types and subtypes of lung cancer, most of which are forms of either non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC). There are differences among these types.

One of the most important may be that smoking remains a top reason for some lung cancers, and is associated with both NSCLC and SCLC types, but many other lung cancers are diagnosed in people who have never smoked.

Radon and other environmental causes may contribute to these cancers. In some cases, particularly among younger people, there may be an underlying genetic reason.

A Word From Verywell

NSCLC tends to grow more slowly than small cell lung cancer and have a better prognosis. That said, long-term survival from any form of lung cancer is higher when found in the earlier stages of the disease.

Lung cancer screening is recommended for people ages 50 to 80 with at least a 20 pack-year history of smoking, and who smoked or quit smoking in the past 15 years.

If you've never smoked, you may still want to ask about screening. A 2019 study in the Journal of Thoracic Oncology found that low-dose computerized tomography (CT) imaging helped find early-stage cancers that would have otherwise been missed in both smokers and never-smokers.