The two types of lung cancer are non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLC accounts for roughly 85% of all lung cancer diagnoses, while SCLC makes up the remaining 15%. The distinction matters because these two types behave differently, respond to different treatments, and carry different outlooks.
Non-Small Cell Lung Cancer (NSCLC)
NSCLC is the far more common type, and it’s actually an umbrella term covering several subtypes. The two most prevalent are lung adenocarcinoma, which represents 50 to 60% of NSCLC cases, and squamous cell carcinoma, which accounts for 20 to 30%. A third, less common subtype called large cell carcinoma makes up most of the remainder.
These subtypes tend to affect different people. Adenocarcinoma is the type most often found in non-smokers and is roughly split between men and women. It typically starts in the outer portions of the lungs and often grows relatively slowly. In many cases, it’s caught at an earlier stage, with tumors averaging around 2 cm at the time of diagnosis. It may show up on imaging as a hazy, ground-glass pattern rather than a solid mass.
Squamous cell carcinoma, by contrast, is strongly linked to smoking. In one large study comparing the two subtypes, 74% of squamous cell patients were smokers compared to just 25% of adenocarcinoma patients, and nearly all squamous cell cases were in men. This subtype tends to grow in the central airways of the lungs, produces more noticeable symptoms early on (cough in about 77% of patients, heavy mucus production in 55%), and is typically larger at diagnosis, averaging around 4.3 cm on imaging.
NSCLC generally grows and spreads more slowly than small cell lung cancer, which is one reason surgery plays a central role in treatment. For early-stage NSCLC, removing the tumor surgically is the most effective option and offers the best chance of a cure. When surgery isn’t possible, focused radiation therapy can sometimes serve as an alternative.
Small Cell Lung Cancer (SCLC)
SCLC is less common but significantly more aggressive. It grows quickly, spreads early, and is almost always linked to heavy smoking. By the time it’s found, it has usually already spread beyond the lung where it started.
Because SCLC behaves so differently, it uses a simpler staging system than NSCLC. Rather than the detailed size-and-spread approach used for NSCLC, doctors classify SCLC as either limited stage or extensive stage. Limited stage means the cancer is still confined to one side of the chest and can be targeted with a single radiation field. Extensive stage means it has spread more widely, whether to the other lung, distant lymph nodes, or other organs. Most people are diagnosed at the extensive stage.
Surgery is rarely an option for SCLC because the cancer has typically spread by the time of diagnosis. Treatment relies heavily on chemotherapy, often combined with radiation. SCLC tends to respond well to chemotherapy initially, but it also tends to come back.
How Diagnosis Works
You can’t tell these two types apart based on symptoms alone. Diagnosis starts with imaging, usually a CT scan, but confirming the type requires a biopsy, where a small sample of tissue is examined under a microscope. In clear-cut cases, a pathologist can identify the cancer type just by looking at the cell structure.
When the cells don’t have obvious features, special staining techniques help sort them. Pathologists test for specific protein markers: one set of markers identifies adenocarcinoma, another identifies squamous cell carcinoma, and a third set flags neuroendocrine features characteristic of SCLC. The goal is to use as few stains as possible so that enough tissue remains for molecular testing, which has become essential for guiding treatment.
Targeted Therapy for NSCLC
One of the biggest differences between the two types is how treatable they are with newer, precision therapies. NSCLC tumors frequently carry specific genetic mutations that drugs can target directly. The most common is a mutation in a gene called EGFR, which is found in 52 to 74% of adenocarcinomas in non-smoking East Asian women and about 10% of smoking-related cases. Another targetable change, called an ALK rearrangement, appears in up to 14% of lung cancers in people who have never smoked.
Altogether, doctors can now test for mutations in at least nine different genes and match patients with therapies designed to block those specific pathways. This approach has meaningfully improved survival for some people with advanced NSCLC, particularly those with adenocarcinoma. SCLC, unfortunately, has far fewer targetable mutations, which is one reason treatment options for it have been slower to advance.
Survival by Stage
Across all types of lung cancer, how early it’s caught is the single biggest factor in survival. For cancer that’s still localized to the lung, the five-year survival rate is 65.5%. Once it has spread to nearby lymph nodes, that drops to 38.2%. For cancer that has reached distant organs, the rate falls to 10.5%.
NSCLC generally carries a better prognosis than SCLC at every stage, largely because it grows more slowly and is more likely to be caught before it spreads. SCLC’s rapid growth means it’s rarely found at the localized stage.
Who Should Be Screened
The U.S. Preventive Services Task Force recommends annual low-dose CT screening for adults aged 50 to 80 who have a smoking history of 20 pack-years or more and who either still smoke or quit within the past 15 years. A pack-year means smoking one pack per day for one year, so someone who smoked two packs a day for 10 years would meet the threshold. Screening stops once you’ve been smoke-free for 15 years or if a health condition limits your life expectancy. Early detection through screening is one of the most effective ways to shift a diagnosis from late stage to early stage, where treatment is far more likely to succeed.