While it’s true that all lung cancers are made up of cells that have run amuck, abnormally growing, replicating, and forming masses in the lungs, there are two distinct categories of lung cancer: Non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). These two groups make up the most common lung cancer types, but there are other lung cancers that don’t fit neatly into either of those boxes. If you’ve recently been diagnosed with lung cancer, and you’re wondering what your type means for your future, read on.
What Are the Most Common Types of Lung Cancer?
If you’ve recently received a lung cancer diagnosis, odds are that it was for either non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC)—the two most common types of the disease. While the names non-small and small cell would have you think their differences are all related to the size of the cancer cell, that’s actually not entirely true.
NSCLC and SCLC have distinct structural and behavioral differences, and thus different treatment protocols as well. Knowing which type you have (and what stage) is critical to ensuring you are getting the best possible treatment.
Getting a handle on all the information out there can feel overwhelming, we know. It’s a lot for anyone who’s been newly diagnosed to digest. To simplify matters, we asked top lung cancer experts for their insights and advice and dug through the medical literature to bring you the most up-to-date, accurate info possible. Here you go: HealthCentral’s soup-to-nuts take on lung cancer types.
What Is Non-Small Cell Lung Cancer?
Non-small cell lung cancer (NSCLC) is far and away the most common type of lung cancer, accounting for up to 85% of all lung cancer cases. To make things more complicated, there are three main types of NSCLC: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. And (we know, we know) there are a few other types of NSCLC on top of that, that occur less frequently. The subtypes of NSCLC are all slightly different and are categorized based on how their cells look under a microscope. Nevertheless, there are several things they share in common:
Growth: NSCLCs generally grow and spread to other parts of the body more slowly than small cell lung cancer.
Location: These cancers arise in the epithelial cells, which are the cells that line the lungs. They most often appear in the center of the lung or along the peripheral (although there are always exceptions).
Causes: Smoking accounts for up to 85% of all NSCLC cases. Environmental and occupational exposures can also cause NSCLC, as can genetic mutations.
Treatments: Non-small cell lung cancer can be treated with surgery, chemotherapy, radiation therapy, targeted therapy, or a combo of all of the above. While chemotherapy tends to be less successful with NSCLC, genetic tests can help determine which patients have the best chance of favorable results.
What Are the Main Types of NSCLC?
Adenocarcinoma, squamous cell carcinoma, and large cell carcinoma all fall under the umbrella of NSCLC. Each subtype develops differently but these cancers are grouped together because they share similar treatment methods and outcomes. Here’s the breakdown:
Up to 40% of NSCLC are adenocarcinoma, making this is the most common type of lung cancer in the U.S. Even though it’s strongly linked to smoking, it’s also the most predominant NSCLC to be diagnosed in non-smokers.
Adenocarcinoma begins in glandular cells, like the ones that secrete mucus, and often develops in the alveoli, tiny air sacs in the lungs. Compared with other lung cancers, this one is more likely to be localized (contained in one area).
Women and people between the ages of 20 and 46 are more likely to have adenocarcinoma than other forms of lung cancer.
Squamous Cell Carcinoma
This type of lung cancer accounts for 25% to 30% of NSCLC and it’s the subtype that’s most associated with smoking. Squamous cell carcinoma (also called epidermoid carcinoma) involves the squamous cells, thin and flat cells that line the inside of the bronchial tubes.
This disease often develops in the center of the lungs or in one of the bronchial airways. Squamous cell lung cancer has the potential to create abnormally high levels of calcium in the blood, which can cause confusion, constipation, and dehydration.
Large Cell Carcinoma
Large cell carcinoma originates from neuroendocrine cells, which are like a hybrid of nerve cells and hormone-secreting cells. This subtype, which accounts for about 5% of NSCLC, is a little trickier than the other lung cancers to diagnose. The diagnosis is given after determining that there are no specific features that make the cancer either squamous cell carcinoma or adenocarcinoma.
Large cell carcinoma can occur in any part of the lung. The bulk of these lung cancers are found in men.
The term large cell carcinoma is sometimes used interchangeably with undifferentiated lung cancer. However, they’re not exactly the same. While large cell carcinoma originates from neuroendocrine cells, undifferentiated lung cancer means that the cell’s origin can’t be determined at all.
Additional NSCLC Types
Some non-small cell lung cancers can be further broken down based on specific genetic mutations that can be uncovered via a biomarker (genomic or molecular) screening. For instance, EGFR positive lung cancer refers to lung cancers that have tested positive for an EGFR (epidermal growth factor receptor) mutation.
This specific mutation is present in roughly 10% of non-small cell lung cancers and it’s found in nearly half of all never-smokers with NSCLC. If a mutation is found, sometimes physicians can tailor treatment decisions to have the greatest impact on that specific mutation.
What Is Small Cell Lung Cancer?
Like large cell carcinoma mentioned earlier, all small cell lung cancers are a type of neuroendocrine tumors. That means that SCLC begins with the neuroendocrine cells in your lungs. These cells are responsible for functions such as helping control air and blood flow in the lungs.
With small cell lung cancer (also called small cell carcinoma or oat cell cancer), there is only one subtype: Combined small cell carcinoma makes up just 2% to 5% of all SCLC. Essentially, this type of lung cancer is mashup of both SCLC and NSCLC.
Although it’s faster-growing and quicker to metastasize, small cell lung cancer is not as prevalent as NSCLC, accounting for just 10% to 15% of all lung cancer cases. SCLC is slightly more common in men than women. Here are some shared characteristics of SCLC:
Growth: SCLC spreads quickly and is more likely to metastasize (spread to other parts of the body) than NSCLC.
Location: SCLC often begin in the bronchi, the main thoroughfare into the lungs in the center of the chest. Sometimes, however, SCLC can appear in the periphery of the lungs.
Causes: Almost all cases of small cell lung cancer are due to smoking. SCLC is extremely rare in never-smokers.
Treatments: Individuals wits SCLC are usually treated with radiation therapy and chemotherapy. Surgery has not been shown to impact outcome in this type of lung cancer.
Are there any other types of lung cancers?
There are a few cancers that develop in the lungs that don’t fit into the NSCLC or SCLC categories. These include:
Carcinoid Lung Tumors
Like small cell lung cancer, carcinoid lung tumors are a type of neuroendocrine tumor. But unlike SCLC, carcinoid lung tumors tend to grow very slowly and rarely metastasize. Carcinoid tumors in the lungs can be divided into two categories:
Typical: slow-growing, often contained to the lungs
Atypical: faster-growing, more likely to metastasize
These cancers are usually treated with surgery. If the tumor cannot be removed, however, chemotherapy will likely be used. (Carcinoid lung tumors may also be noncancerous.)
Salivary Gland-Type Lung Carcinomas
This very rare lung cancer was formally dubbed bronchial adenomas and includes adenoid cystic carcinomas and mucoepidermoid carcinomas of the lung. Salivary gland-type carcinomas are thought to start in glands of the airways. These cancers are often treated surgically and sometimes with chemotherapy as well.
Another not-so-common cancer, pleuropulmonary blastoma either grows in the lungs themselves or in the pleura, a thin membrane that lines the surface of the lungs. This cancer affects mostly children and has zero connection to adult lung cancer or its causes. Technically, this is a soft tissue cancer (aka sarcoma), not lung cancer.
This rare cancer develops in the pleura, which is the thin membrane that separates the lung from the chest wall. Exposure to asbestos is the usual cause.
And that completes your tour through some of the common—and not-so-common—types of lung cancer. If you’ve recently been diagnosed, most likely you have either NSCLC and SCLC or a subtype therein. It’s scary, we know, to receive news like this, and it’s natural to worry about what happens next. Try to find some peace is knowing that, because lung cancer is one of the most common cancers, a lot of research has been done on treatment. Your doctor will talk with you about the best path forward, and we’ll be here to answer your questions along the way.