There are two main types of lung cancer—small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Both types form in the tissues of the lungs and the main risk factor is smoking. NSCLC is the more common type, accounting for approximately 85% of cases. SCLC, on the other hand, accounts for the remaining 15% of cases.
Oncologists determine which type of lung cancer a patient has by looking at the cells through a microscope. The various types of lung cancer all display different characteristics; for instance, small cell lung cancer is so named because the tumors are composed of smaller cells. Additionally, each subtype has different growth patterns and responds differently to therapy, so it is important to consider the histological (cell) type before creating a treatment plan.
Non-Small Cell Lung Cancer Subtypes
Non-small cell lung cancer has three unique subtypes:
- Adenocarcinoma – The most common subtype of non-small cell lung cancer, which typically grows in the outer parts of the lung. Adenocarcinomas are often diagnosed in earlier stages and have more positive prognoses than other types of lung cancer. This subtype is especially prevalent in women and is the most common type of lung cancer in patients who do not smoke.
- Squamous cell (epidermoid) carcinoma – The second most common subtype of non-small cell lung cancer, which often develops in the middle of the lungs inside one of the bronchi (airways). Squamous cell carcinomas are very slow growing, but can eventually form a cavity within the lung. This subtype is most frequently diagnosed in men.
- Large cell (undifferentiated) carcinoma – The least common subtype of non-small cell lung cancer, which can appear in any part of the lung. Large cell carcinomas are fast growing and likely to spread, which makes this subtype more challenging to treat.
In a very small percentage of cases, a non-small cell lung cancer can have a different subtype, such as adenosquamous carcinoma or sarcomatoid carcinoma.
Small Cell Lung Cancer Subtypes
Small cell lung cancer is the other main type of lung cancer. These faster-growing lung cancers are occasionally referred to by other names, such as oat cell cancer, oat cell carcinoma, and small cell undifferentiated carcinoma. Small cell lung cancers can be classified as:
- Small Cell Carcinoma – This is the standard diagnosis that encompasses the majority of small cell lung cancer cases. The individual cells look small and flat underneath a microscope.
- Combined Small Cell Carcinoma – This is a less common type of small cell lung cancer, which occurs when a tumor is primarily made up of small cell carcinoma cells and also contains a small number of non-small cell lung cancer cells.
Small cell lung cancers typically originate in the bronchi near the center of the chest. From there, the tumors often spread to nearby lymph nodes or other organs. This tendency makes these types of lung cancer more challenging to treat.
Medically reviewed by Dr. Michael Shafique.
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