Most Common Type of Lung Cancer

The most common type of lung cancer overall is non-small cell lung cancer, with small cell lung cancer less common and decreasing in incidence. There are three different types of non-small cell lung cancer, of which lung adenocarcinoma is most common. Yet the types and subtypes of lung cancer can vary based on age, sex, and smoking status. There has also been a change in the common types of lung cancer over time.

Talking about types of lung cancer, however, can be misleading. We now that no two lung cancers are alike, and are finding some ways in which they are different. For example, two people with lung adenocarcinoma may have very different treatment options, as well as prognosis, based on the molecular profile of their tumor. Let's look at the types of cancer overall, specific groups, and then the importance of knowing the genetic profile of your tumor before starting treatment.

There are two major types of lung cancer. Non-small cell lung cancer is the most common type of lung cancer overall accounting for roughly 80 percent of lung cancers. Small cell lung cancers are responsible for around 15 percent of lung cancers in the United States. Carcinoid tumors are less common, accounting for 5 percent or less of lung tumors.

Non-small cell lung cancers are in turn broken down into 3 types.

• Lung Adenocarcinoma (Accounting for 50 percent of non-small cell lung cancers)
• Squamous Cell Carcinoma of the Lungs (Responsible for around 30 percent of non-small cell lung cancers)
• Large Cell Lung Cancer (Responsible for about 10 percent of non-small cell lung cancers)

Non-small cell lung cancers are found much more commonly among women. These tumors are also the most common type of lung cancer in men, but men are more likely than women to develop small cell lung cancer.

Of non-small cell lung cancers, lung adenocarcinomas occur more frequently in women, while squamous cell and large cell lung cancers are more likely to occur in men.

Lung adenocarcinoma is the most common type of lung cancer in young adults—accounting for roughly 80 percent of these cancers (small cell lung cancers are very uncommon). Young adults with lung cancer are much more likely to have a genetic predisposition to lung cancer and a higher likelihood of treatable mutations (see below).

Carcinoid tumors of the lung tend to be found in younger people than the more common types of lung cancer, and are the most common type of lung tumors found in children.

In many ways, lung cancer in non-smokers is a different disease than lung cancer in people who smoke, and this includes the most common types of the disease.

Both non-small cell and small cell lung cancers are linked with a history of smoking, though small cell lung cancer is associated much more strongly with smoking. Non-small cell lung cancers are the form of lung cancer found more frequently in individuals who have never smoked.

Of non-small cell lung cancers, lung adenocarcinoma is the type most likely to be found in non-smokers. Squamous cell carcinoma less common than lung adenocarcinoma overall, but is more common in people who have smoked.

Carcinoid tumors do not appear to be associated with smoking, and are found in smokers and non-smokers in a ratio similar to the general population.

There is a theory that the addition of filters to cigarettes in years back may have affected the types of lung cancer found. Cancers such as small cell lung cancer and squamous cell lung cancer tend to occur in or near the largest airways and were more common before the addition of filters to cigarettes. When filters became commonly used in cigarettes, cancers found more in the periphery of the lungs such as lung adenocarcinoma became more common, It's thought that the carcinogens in tobacco smoke were deposited in the large airways before the advent of filters, but are carried much deeper into the lungs with the addition of filters.

It's now recommended that anyone with non-small cell lung cancer have molecular profiling or genetic testing. With next generation sequencing there are now many treatable mutations, meaning mutations found in lung tumors for which treatment is available. With lung cancer this includes EGFR, ROS1, ALK, BRAF, MET, RET, and HER2.

Tumors that have treatable mutations are more commonly found in young adults, never smokers, and women, though they can be found in almost anyone.

Non-small cell lung cancer tends to grow more slowly than small cell lung cancer and have a better prognosis.That said, long-term survival from either form of lung cancer is higher when found in the earlier stages of the disease. Lung cancer screening is now available for people who have smoked at least 30-pack years, and hopefully screening will be available for never smokers in the future. For now it's important to know that anyone with lungs can get lung cancer, and lung cancer in never smokers is the sixth leading cause of cancer-related deaths in the United States.