Lung cancer is classified into two types, each of which is treated differently.

Non-small cell lung cancer (NSCLC) (NSCLC)
NSCLC accounts for approximately 80% to 85% of all lung cancers. NSCLC is classified into three subtypes: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. These subtypes, which arise from various types of lung cells, are grouped together as NSCLC because their treatment and prognosis (outlook) are frequently similar.

Adenocarcinoma: Adenocarcinomas begin in cells that normally secrete substances like mucus.

This type of lung cancer is most common in people who smoke or have smoked in the past, but it is also the most common type of lung cancer seen in people who do not smoke. It is more common in women than in men, and it occurs at a younger age than other types of lung cancer.

Adenocarcinoma is more likely to be discovered in the outer parts of the lung before it has spread.

People with adenocarcinoma in situ (previously known as bronchioloalveolar carcinoma) have a better prognosis than those with other types of lung cancer.

Squamous cell carcinoma: Squamous cell carcinomas begin in squamous cells, which are flat cells that line the inside of the lungs’ airways. They are frequently associated with a history of smoking and are typically found in the central part of the lungs, near a major airway (bronchus).

Large cell (undifferentiated) carcinoma: This type of cancer can develop in any part of the lung. It grows and spreads quickly, making treatment more difficult. Large cell neuroendocrine carcinoma, a subtype of large cell carcinoma, is fast-growing cancer that is very similar to small cell lung cancer.

Other subtypes: Adenosquamous carcinoma and sarcomatoid carcinoma are two less common subtypes of NSCLC.

Lung cancer with small cells (SCLC)
SCLC accounts for 10% to 15% of all lung cancers and is also known as oat cell cancer.

This type of lung cancer grows and spreads more quickly than NSCLC. At the time of diagnosis, approximately 70% of people with SCLC will have cancer that has already spread. Because this cancer spreads quickly, it responds well to chemotherapy and radiation therapy. Unfortunately, for the vast majority of people, cancer will reoccur at some point.

Cancer develops when the body’s cells begin to proliferate uncontrollably.

In your chest, you have two sponge-like organs called lungs. Your right lung is divided into three sections known as lobes. Your left lung is made up of two lobes. Because the heart takes up more space on that side of the body, the left lung is smaller.

When you breathe in, air enters your mouth or nose and travels to your lungs via the trachea (windpipe). The trachea divides into bronchi, which enter the lungs and divide further into smaller bronchi. These divide into smaller branches known as bronchioles. Alveoli are tiny air sacs located at the end of the bronchioles.

When you exhale, the alveoli absorb oxygen from the inhaled air and remove carbon dioxide from the blood. The primary functions of your lungs are to take in oxygen and expel carbon dioxide.

Lung cancer usually begins in the cells that line the bronchi and other parts of the lung, such as the bronchioles or alveoli.

The pleura is a thin lining layer that surrounds the lungs. The pleura protects your lungs and allows them to slide back and forth against the chest wall as you breathe.

The diaphragm, a thin, dome-shaped muscle located beneath the lungs, separates the chest from the abdomen. The diaphragm moves up and down when you breathe, forcing air into and out of the lungs.