Small-Cell and Non-Small-Cell Lung Cancer: What’s the Difference?

Medically Reviewed by Sabrina Felson, MD on July 24, 2022
6 min read

Lung cancer is the leading cause of cancer deaths among both men and women. Small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) are the two main types of lung cancer. Most lung cancers are NSCLC. Only about 15% of lung cancers are SCLC.

Their names stem from what their cells look like when you look at them under a microscope. SCLC cells look round and undersized in comparison to NSCLC cells. But the big difference is how aggressive they are. SCLC is more aggressive than NSCLC and often spreads to other parts of your body.

Here are the facts about SCLC and NSCLC and how they differ.

Small-cell lung cancer is when abnormal cells in your lung grow fast and uncontrollably. It’s an aggressive form of cancer that often starts in your airways and then spreads, or metastasizes, to other parts of your body.

There are two types of SCLC, which are based on which cells are affected:

  • Small-cell carcinoma, which is also called oat cell cancer, is the more common type of SCLC.
  • Combined small-cell carcinoma is a rare type of SCLC that has both SCLC and NSCLC components.

For most people, by the time you’re diagnosed with SCLC, it has already spread to other parts of your body. The areas may include:

  • Adrenal glands
  • Bone marrow
  • Bones
  • Brain
  • Liver
  • Lymph nodes

Non-small-cell lung cancer is when cancer cells form in your lung tissues. It’s more common and less aggressive than SCLC. But it’s important to catch it early so it doesn’t spread to other areas.

The most common types of NSCLC are:

  • Adenocarcinoma, which starts in the mucus-producing cells lining your smallest airways
  • Large cell carcinoma, which starts in neuroendocrine cells in the lung
  • Squamous cell carcinoma, which starts in flat cells lining the larger airways

The main difference between SCLC and NSCLC is how aggressive they are. Another difference is how common they are. NSCLC is a less aggressive and more common form of lung cancer than SCLC.

Your doctor will know which type of lung cancer you have when they take a biopsy, or small sample of the tumor, and send it to a lab, where scientists will examine it under a microscope. They’ll also see where the cancer started and how abnormal the cells are.

It’s possible you won’t notice any symptoms of lung cancer, especially in the early stages. It’s common for doctors to find lung cancer when they do an X-ray for something else.

When present, symptoms of SCLC and NSCLC are similar:

  • Appetite loss or weight loss
  • Chest discomfort
  • Worsening cough
  • Coughing up blood
  • Hoarseness
  • Swelling of your face and neck veins
  • Tiredness
  • Trouble breathing
  • Trouble swallowing

Because SCLC is more likely to metastasize (or spread) early on, you may have symptoms that stem from lung cancer in other organs. They may include:

  • Bone pain
  • Bumps or lumps in your skin
  • Confusion
  • Paralysis
  • Seizures

The main risk for both SCLC and NSCLC is smoking. About 98% of SCLC cases are linked to smoking tobacco. This includes cigarettes, pipes, and cigars.

The earlier you start smoking, the longer you smoke, and the more often you smoke, the higher your risk is. If you already smoke, quitting now lowers your chances of developing lung cancer.

It’s best to avoid secondhand smoke, too, because it’s also a risk factor.

Other risk factors for SCLC include:

  • Environmental pollution
  • Radiation
  • Workplace carcinogens
  • Family history of lung cancer
  • HIV infection

Other risk factors for NSCLC include:

  • Workplace exposure to asbestos, arsenic, chromium, beryllium, nickel, soot, or tar
  • Radiation therapy to your breast or chest
  • Radon
  • Imaging tests like CT scans
  • Atomic bomb radiation
  • Environmental pollution
  • Family history of lung cancer
  • HIV infection
  • Being a heavy smoker and taking beta-carotene supplements

The more risk factors you have, the higher chance you have of developing lung cancer.

Lung cancer develops and progresses quickly. This is why it is often diagnosed at an advanced, incurable stage. Screening for lung cancer has been introduced for high-risk people in order to catch lung cancers early when there is still a chance of cure.

If you have a history of smoking, your doctor may do regular CT screenings. The American Society of Clinical Oncology recommends annual screenings if you’re 55-74 and smoked one or more packs of cigarettes a day, for 30 years or more, even if you quit.

The U.S. Preventive Services Task Force recommends annual screenings with a low-dose CT scan every year if you’re 50-80 with a 20 pack-year history and you still smoke or you quit within the last 15 years. Screenings can stop when you’ve been smoke-free for 15 years or have a health problem that limits your treatment options or life expectancy.

Lung cancer screening for high-risk people is helpful because SCLC grows fast and it’s rare that it’s diagnosed before you notice symptoms. Survival depends on early diagnosis.

If your doctor is worried about lung cancer, they may:

  • Look for general signs of health
  • Ask about symptoms of cough, weight loss, and shortness of breath
  • Check for enlarged lymph nodes
  • Ask about your smoking history
  • Ask about other illnesses and treatments you’ve had
  • Ask about your job and past jobs

They may also run tests and scans, including:

  • Blood tests
  • Chest X-ray
  • CT scan
  • MRI
  • PET scan

If they think you have lung cancer, they’ll take a biopsy of the abnormal area in the lung to evaluate for cancer cells.

There are different options for treating lung cancer. The treatment you get depends on the type and stage of your lung cancer, and other factors like your age and overall health.

Lung cancer treatment may include:

  • Chemotherapy
  • Immunotherapy
  • Radiation therapy
  • Surgery
  • Targeted drug therapy

The most common type of treatment for SCLC is chemotherapy. Your doctor may recommend combining it with radiation.

If you have NSCLC and it hasn’t affected a large part of your lungs or spread to other areas of your body, your doctor may recommend surgery to remove the cancer cells.

You may consider joining a clinical trial. This is a study done to research lung cancer and find out if new treatments are safe and effective, or if they’re better than standard treatment.

Some clinical trials may offer a better treatment for your cancer. Talk to your doctor about options.

The outlook for NSCLC is better than SCLC.

Most people find out they have SCLC when it’s already spread to other parts of their body. Early detection helps, but it’s often found late because you may not have symptoms.

With SCLC, the 5-year survival rate is less than 5%. Without treatment, survival is about 2 to 4 months. With treatment, it’s longer. If you have chemotherapy, it may be about 10 months. Even if treatment is successful, the cancer often comes back.

For men, SCLC is the leading cause of cancer-related death. For women, it’s the second most common cause of cancer-related death.

Your chance of survival is higher for NSCLC, but it depends on a variety of factors. They include:

  • The lung cancer stage, which is based on tumor size and whether or not it spread to other areas
  • The type of NSCLC you have
  • Whether or not it mutated, or changed, in certain genes
  • Your overall health
  • Your signs and symptoms

The 5-year relative survival rate for NSCLC may range from 64% if you catch it early and it hasn’t spread outside your lung, to 8% if it has spread to other areas of your body like your brain, bones, liver, or other lung.

For SCLC, the 5-year relative survival rate may range from 29% in early stages to 3% if it has spread to other parts of your body.