The Difference Between Small Cell and Non-Small Cell Lung Cancer

Lung cancer is the third most common cancer after skin cancer, prostate cancer (in men), and breast cancer (in women). The American Cancer Society estimates that more than 235,000 people in the United States will receive a new diagnosis of lung cancer in 2021, with the disease claiming nearly 132,000 lives. Lung cancer primarily occurs in older individuals, with the average age of patients being 70 years. The disease is rare in people younger than 45.

Receiving a lung cancer diagnosis can be overwhelming and confusing. Learning more about the disease, including its major types, can help you understand it better. Please continue reading to learn about the different types of lung cancer.

What are the types of lung cancer?

The two main types of lung cancer are called small cell lung cancer and non-small cell lung cancer. This definition is based on how the cancer cells appear under the microscope. The symptoms of the two are often very similar. However, lung cancer treatment for these two types of diseases can be very different.

Non-small cell lung cancer (NSCLC)

Incidence: This is the overwhelmingly more common form of the disease. About 85% of lung cancers are non-small cell lung cancers.

Location: Non-small cell lung cancers can be located in the mid-chest as well as in other parts of the lungs.

Cause: Smoking is a common cause but NSCLC can also occur in non-smokers and never smokers.

Survival: The 5-year survival rate for stage 1 NSCLC (localized tumor) is 63%. Later stages of NSCLC have a 5-year survival rate of 35% (regional spread) and 7% (distant spread). The survival rate of NSCLC (all stages combined) is 25%. This means people with NSCLC, on average, are 25% as likely to live for 5 years compared to people who don’t have cancer.

Types: The subtypes of NSCLC develop from different types of lung cells, but they have a similar treatment and prognosis (outlook) and are therefore grouped together as NSCLC.

Adenocarcinoma: This type of cancer makes up around 70% of non-small cell lung cancer. It starts in mucus-secreting cells in the lungs. One of the major risk factors for adenocarcinoma is a history of smoking, but it is also the most common type of lung cancer found in non-smokers. Adenocarcinoma is more common in women than men and tends to occur in younger people compared to other types of lung cancer. The location of the tumor is usually in the outer parts of the lung. Adenocarcinomas have a good prognosis as they are often discovered before they have spread.

Squamous cell carcinoma: This type of cancer starts in the squamous cells, which are flat cells that line the insides of the airways. Squamous cell carcinomas often occur in current and former smokers. The location is usually in the central lung near the main bronchus (airway).

Large cell carcinoma: This is a type of non-small cell lung cancer that can occur anywhere in the lungs. It grows and spreads quickly and is difficult to treat. A type of fast-growing large cell cancer called large cell neuroendocrine carcinoma is very similar to small cell lung cancers.

Other types of NSCLC: There are some less common types of non-small cell lung cancers such as sarcomatoid carcinoma and adenosquamous carcinoma.

Small cell lung cancer (SCLC)

Incidence: Roughly 10 to 15% of all lung cancers are small cell lung cancers. The majority of SCLC are oat cell cancers.

Location: SCLC tends to grow more centrally in the mid-chest.

Cause: Almost all cases of SCLC are due to tobacco smoking. SCLC is very rare in people who have never smoked.

Survival: The 5-year survival rate for SCLC stage 1 (localized) is 27%, stage 2 (regional spread to lymph nodes) is 16%, and stage 3 (distant spread) is 3%. The survival rate for all stages of SCLC combined is 7%.

Small cell lung cancer is typically a more aggressive type of lung cancer that grows and spreads rapidly. SCLC is found to have spread outside the lungs in approximately 70% of patients by the time they are diagnosed. Because it is a fast-growing cancer, it responds well to chemotherapy and radiation therapy. However, it can, unfortunately, return after treatment.

Other types of lung cancers

Other types of lung tumors such as slow-growing lung carcinoid tumors, adenoid cystic carcinomas, sarcomas, and lymphomas are rare and account for fewer than 5% of all lung carcinoma.

Besides primary lung tumors which start in the lungs, other types of cancers can spread to the lungs (for example, cancers that start in the skin, pancreas, breast, or kidney). This is known as metastasis or secondaries. Cancer that starts in the breast and spreads to the lung is classified as breast cancer and treated as such.

Which is worse, small cell or non-small cell lung cancer?

Some types of non-small cell lung cancer can be more aggressive, but in general, SCLCs are more aggressive than NSCLCs. In other words, small cell lung cancers are less common but they grow and spread more rapidly.

Is non-small cell lung cancer the same as large cell lung cancer?

Large cell carcinoma is a subtype of non-small cell lung cancer. It is the least common type of NSCLC and tends to grow and spread rapidly.

Which type of lung cancer is the most aggressive form?

Although they make up only 15% of lung cancer cases, small cell lung cancers are the most aggressive type. This cancer usually starts in the bronchi (airways) in the center of the chest and grows rapidly to form a large tumor. The tumor often spreads quickly (metastasizes) to nearby lymph nodes and other parts of the body such as the brain, bone, and liver.

Can non-small cell lung cancer turn into small cell lung cancer?

Approximately 5-10% of lung cancers are combined small cell and non-small cell. Research suggests that these mixed tumors may be easier to treat than small cell lung cancer. Additionally, lung cancer treatment with certain immunotherapy drugs called tyrosine kinase inhibitors (nivolumab, pembrolizumab) can lead to the transformation from non-small cell lung cancer to small cell lung cancer.

Lung cancer is a complicated disease. It is much more than just small cell or non-small cell lung cancer. Every year, new drugs are approved to treat lung cancer, and the average doctor may not be up-to-date with the newest therapies and treatment options available. That’s why it is important to be medically reviewed at a major academic medical center if you have received a lung cancer diagnosis or see someone who has the latest information about the specific form of lung cancer you have.

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