Lung cancers develop in cells that line the bronchi and in a part of the lung tissue called the alveoli, which are air sacs where gases exchange. Changes to DNA cause cells to grow more rapidly.
There are two main types of lung cancer:
Keep reading to find out more about the similarities and differences between these two types.
Approximately 10 to 15 percent of lung cancer cases are SCLC.
SCLC usually starts near the center of the chest around the bronchi. It’s a fast-growing form of cancer that tends to spread in its early stages. It tends to grow and spread much faster than NSCLC.
SCLC is rare in nonsmokers.
Approximately 80 to 85 percent of lung cancer cases are NSCLC. There are three types of NSCLC:
- Adenocarcinoma is a primary lung cancer that’s usually located in the periphery of the lung. A subtype of this cancer called adenocarcinoma in situ (previously known as bronchoalveolar carcinoma) is slow growing and most commonly seen in nonsmokers.
- Squamous cell carcinoma generally occurs in the center of the lung. It tends to develop in smokers and can be associated with elevated calcium levels in the blood.
- Large cell carcinoma occurs anywhere in the lung, and it usually grows and spreads at a rapid rate.
Early stage lung cancer doesn’t usually produce obvious symptoms. As the cancer progresses, there may be:
- shortness of breath
- coughing up blood
- chest pain
Other symptoms may include:
- fatigue and weakness
- loss of appetite and weight loss
- difficulty swallowing
- pain in the bones and joints
- swelling of the face or neck
Smoking is the biggest risk factor for both SCLC and NSCLC.
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Other causes and risk factors include:
- secondhand smoke
- exposure to radon
- exposure to workplace chemicals like asbestos, arsenic, and diesel exhaust
- family history
The first step in diagnosing lung cancer is a physical examination. If your doctor suspects lung cancer, they may recommend further testing.
- Imaging tests. X-ray, MRI, CT, and PET scans can all detect abnormal masses in the lungs.
- Sputum cytology. The cells of your phlegm can be examined under a microscope if you produce phlegm when you cough.
- Biopsy. If other tests show that masses in the lungs are present, a biopsy can determine if these masses contain cancerous cells. Biopsy types include needle, bronchoscopy, and mediastinoscopy.
Cancer may spread from the original tumor to other parts of the body. This is called metastasis.
There are three ways this can happen:
- Cancer can invade nearby tissue.
- Cancer cells can travel from the primary tumor to nearby lymph nodes. They can then travel through the lymphatic system to reach other parts of the body.
- Once cancer cells enter the bloodstream, they can travel anywhere in the body (hematogenous spread).
A metastatic tumor that forms somewhere else in the body is the same type of cancer as the original tumor.
The Tumor, Node, Metastasis (TNM) staging system for NSCLC is an internationally accepted system used to characterize the extent of disease.
The TNM system combines features of the tumor into disease stage groups 1 to 4, with stage 4 being the most severe. TNM staging correlates with survival and are linked to recommendations for treatment.
Earlier-stage cancers have a better outlook than later-stage cancers.
Since SCLC is so aggressive, its staging is not based on traditional TNM stages. It’s staged and managed using a simplified system of clinical limited or clinical extensive disease.
Treatment depends on many factors, including stage at diagnosis. If the cancer hasn’t spread, removing a part of the lungs may be a first step.
Surgery, chemotherapy, and radiation may be used alone or in some combination. Other treatment options include laser therapy and photodynamic therapy.
Other medications may be used to alleviate individual symptoms and side effects of treatment. Treatment is tailored to individual circumstances and may change accordingly.
The outlook varies according to:
- cancer type
- stage at diagnosis
- treatment response
- an individual’s age and overall health
In general, survival rates are higher for earlier-stage (stage 1 and 2) lung cancers. Treatments are improving with time.
Five-year survival rates are calculated based on people who’ve received treatment at least 5 years ago. The 5-year survival rates shown below may have improved as of current research.
While SCLC is much more aggressive than NSCLC, finding and treating all lung cancers early is the best way to improve a person’s outlook.