Lung Cancer: Understanding the Basics

Cancer may seem complex. But at its core, cancer is simple. Normal cells grow and die when your body needs them to. Cancer is what happens when certain cells grow even though your body doesn’t need them.

In many cases, these cancerous cells form a lump or mass called a tumor. Since cancerous cells don’t act like normal cells, tumors can prevent your organs from working properly. Given time, they can also spread, or metastasize, to other parts of the body.

Lung cancer is cancer that starts in the cells that make up the lungs. It isn’t cancer that spreads to the lungs from other parts of the body. This is key because treatment is based on the original site of the tumor. For example: If a tumor begins in the breast and spreads to the lungs, it would be treated as metastatic breast cancer—not lung cancer.

Types of lung cancer

There are 2 main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Knowing the differences between the two will help you understand more about your diagnosis and treatment.

Non-small cell lung cancer

NSCLC accounts for 80% to 85% of lung cancer cases. There are 3 main subtypes. Each subtype is named for the type of cell it develops in:

• Adenocarcinoma. This is the most common type of lung cancer—particularly among the minority of non-smokers who get the disease. It tends to appear on the outer areas of the lungs and grows more slowly than the other subtypes.

• Squamous cell carcinoma. This type of cancer develops more often in smokers or former smokers. It tends to start in the center of the lungs near the bronchial tubes.

• Large cell carcinoma. The least common of the 3 subtypes of NSCLC, large cell carcinoma can begin anywhere in the lung. It tends to grow more quickly than the other two subtypes, which can make it harder to treat.

Despite differences, the treatment approach is often similar.

Small-cell lung cancer

Only 10% to 15% of people diagnosed with lung cancer have small-cell lung cancer (formerly called oat cell cancer). It is also almost exclusively found in people who smoke or previously smoked. It tends to grow more quickly than NSCLC. It often spreads earlier to other parts of the body such as chest and neck lymph nodes and the brain.

How lung cancer spreads

Lung cancer acts differently in different people. But when it spreads, it tends to go to the same place first: lymph nodes in the center of the chest. It may also spread to lymph nodes in the lower neck.

Lymph nodes are small clusters of immune system cells. If affected, they can help your healthcare team understand the extent of the cancer. This can determine the course of treatment—and possibly prevent the cancer from advancing.

During later stages, lung cancer may spread to more distant parts of the body, such as the liver, brain, or bones.

Lung cancer causes

Smoking is still the leading cause of lung cancer. The Centers for Disease Control and Prevention says smoking accounts for 80% to 90% of all lung cancer cases. To people who smoke, this can sound like a scary statistic. But it’s worth noting that quitting smoking now, even after years of heavy use, can greatly reduce your risk of getting lung cancer. If you’re a smoker who wants to quit, ask your healthcare provider for help. The CDC has additional resources at www.cdc.gov/tobacco/quit_smoking/index.htm.

Lung cancer screenings

There is no routine screening for lung cancer for people who don't have any signs or symptoms. The American Cancer Society recommends yearly screening for lung cancer with a low dose CT (LDCT) scan for people aged 50 to 80 who smoke or used to smoke. Discuss with your healthcare provider the benefits, limits or possible harm of this screening for you.

Lung cancer symptoms

Symptoms of lung cancer vary and can overlap with other conditions. Talk with your healthcare provider if you have the following:

• Coughing persistently or coughing up bloody mucus

• Wheezing

• Feeling short of breath

• Having ongoing chest pain or upper back pain

• Suffering from severe fatigue

• Lung infections that don't go away or come back often

• Headache, trouble walking, change in coordination

• Losing weight without explanation

Your symptoms can help your provider find the cause.