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

There are two main types of lung cancer: small cell lung cancer and non-small cell lung cancer. Each type looks, grows, and spreads differently. They are also treated in different ways.

This article discusses the differences between small cell lung cancer and non-small cell lung cancer.

What Is Small Cell Lung Cancer (SCLC)?

Like its name suggests, small cell lung cancer contains cells that are smaller in size. SCLC usually starts in the bronchi, located in the middle of the chest. It’s sometimes referred to as “oat cell cancer” because under a microscope, its oval-shaped cells look like grains of oat.

SCLC tends to grow and spread in the body quickly, but usually responds well to chemotherapy and radiation. Most people are diagnosed with SCLC when the disease has already spread.

There are two sub-types of SCLC: small cell carcinoma and combined small cell carcinoma. These groups are categorized based on how their cells look under a microscope.

• Small cell carcinoma is the most common type of SCLC. The cells of a small cell carcinoma tumor look flat under a microscope.
• Combined small cell carcinoma is a tumor that’s made up of some small cell carcinoma cells and some non-small cell lung cancer cells.
  

What Is Non-Small Cell Lung Cancer (NSCLC)?

Non-small cell lung cancer affects the cells lining the surface of the lung’s airways. NSCLCs are usually more slow-growing than SCLCs. The cells of a NSCLC tumor are typically larger in size.

There are three main subtypes of NSCLC: adenocarcinomas, squamous cell carcinomas, and large cell carcinomas.

Adenocarcinoma

Adenocarcinomas often start in the outer region of the lung, in glands that would normally secrete mucus to help you breathe. They’re the most common form of lung cancer.

About 30% of all lung cancers and 40% of NSCLCs are adenocarcinomas.

Squamous Cell Carcinoma

Squamous cell carcinomas, also called epidermoid carcinomas, are the second most common type of NSCLC. They start in the squamous cells, which are thin, flat cells that line the inside of the airways.

About 25% to 30% of NSCLCs are squamous cell carcinomas.

Large Cell Carcinoma

Large cell carcinomas are a rare form of NSCLC, which only represent about 10% to 15% of all cases. This type of lung cancer can occur anywhere in the lung and is usually aggressive.

Other Types

There are other, more rare forms of lung cancer. In some cases, if your cancer cells look undeveloped under a microscope, healthcare providers might not be able to tell you exactly what type you have.

Small Cell vs. Non-Small Cell Lung Cancer

SCLC and NSCLC share some similarities, but also some important differences.

In general, SCLCs are more aggressive and have a poorer prognosis, but your outlook greatly depends on when the cancer is detected.

Causes and Risk Factors

Anyone can develop lung cancer, but the disease is much more common among smokers. In fact, smoking is the number one risk factor for lung cancer. Researchers estimate that as many as 90% of lung cancers could be prevented if people didn’t smoke cigarettes.

While smoking is an important risk factor for both SCLC and NSCLC, it seems to be linked more closely to SCLC. Nearly all cases of SCLC are due to smoking.

Other risk factors for lung cancer include:

• Exposure to substances like radon, asbestos, arsenic, nickel, tar, or other agents
• Older age
• Having a family history of lung cancer
• Exposure to air pollution or secondhand smoke
• Having radiation therapy to the lungs
  

Prevalence

Lung cancer is the second most common cancer type in both men and women and is the leading cause of cancer-related death. In 2021, an estimated 253,760 adults in the United States will develop lung cancer.

NSCLC is the most common form of lung cancer, representing about 80% to 85% of all cases. SCLC is a rarer type, accounting for only about 13% to 15% of all lung cancers.

Symptoms

Symptoms of NSCLC and SCLC usually don’t show up until the cancer has spread in the body.

Some signs to watch out for include:

• A persistent cough
• Coughing up blood or rust-colored phlegm
• Chest pain that worsens when you cough, laugh, or breathe
• Loss of appetite
• Unexplained weight loss
• Hoarseness
• Shortness of breath
• Feeling very tired or weak
• An infection that won’t go away or keeps coming back
• Wheezing
  

Diagnosis

Healthcare providers use different methods to diagnose lung cancer, including:

• Imaging tests: This may include an X-ray, CT scan, MRI, PET scan, or other test.
• Sputum cytology: Healthcare providers examine phlegm under a microscope to look for cancer cells.
• Pulmonary function tests: These tests usually involve breathing in and out of a tube to measure your airflow.
• Biopsy: A small piece of tissue is removed from your lung and examined under a microscope.

Healthcare providers usually rely on a biopsy to help them determine if the lung cancer is NSCLC or SCLC.

Stages

After a lung cancer diagnosis, your healthcare provider will try to determine your cancer’s stage, or how much it has spread throughout your body.

Staging for NSCLC involves using a numeric system that ranges from 0-4. The lower the number, the less the cancer has spread.

Healthcare providers may also use a letter “T,” “N,” or “M” with a number or letter after them to describe the cancer. These letters stand for:

• T (tumor): Describes your tumor’s size and where it’s located
• N (node): Reveals if your cancer has spread to your lymph nodes
• M (metastasis): Tells healthcare providers if your cancer has spread to other parts of your body

The staging system for SCLCs is typically less complex. It classifies the cancer into two main categories, which include:

• Limited: This means the cancer is found on one side of the chest and may include nearby lymph nodes.
• Extensive: This describes lung cancer that’s spread widely throughout the lung, both lungs, or other areas of the body.

Sometimes, the TNM staging method might also be used for SCLCs.

Treatment

The treatments you receive might depend on whether you have SCLC or NSCLC.

In most cases, SCLC has already spread by the time it’s discovered, so healthcare providers treat it aggressively. Chemotherapy is often the main treatment choice for people with SCLC.

Other options for SCLC may include:

• Radiation
• Immunotherapy
• Surgery (this is rarely an option, but can be done if the cancer is found early)

NSCLC is less aggressive than SCLC, but it’s also not often caught at an early stage.

Some treatment options for NSCLC include:

• Surgery
• Radiofrequency ablation (using high-energy radio waves to heat a tumor)
• Radiation
• Chemotherapy
• Targeted drugs
• Immunotherapy
  

Outlook

Survival rates are different for SCLC and NSCLC. In general, a person with SCLC usually has a poorer outlook, but this depends on when the cancer is diagnosed, an individual’s overall health, and the treatments they receive.

According to the American Cancer Society, the five-year survival rate for all stages of NSCLC is 25%, while the five-year survival rate for all stages of SCLC is 7%.

Summary

Lung cancer is a complex disease that includes different types and subtypes. Non-small cell lung cancer and small cell lung cancer are the two main forms. While they share some similarities, distinct characteristics set them apart. Small cell lung cancer is usually more aggressive with a poorer outlook than non-small cell lung cancer.

A Word From Verywell

Being diagnosed with lung cancer can be scary, but arming yourself with information may help you fight the disease. Talk to your healthcare provider or oncologist about the type of lung cancer you have and how best to treat it. Remember that statistics are only statistics and don’t represent your individual case.