Lung Cancer Quick Overview
Lung cancer is a group of diseases characterized by abnormal growths (cancers) that started in the lungs.
Lung cancer is the leading cause of cancer deaths in women and men both in the United States and throughout the world. Lung cancer has surpassed breast cancer as the leading cause of cancer deaths in women for the past 25 years. In the United States, there are more deaths due to lung cancer than the number of deaths from colon and rectal, breast, and prostate cancer combined.
If lung cancer is found at an early stage, at least half of such patients will be alive and free of recurrent cancer five years later. Once lung cancer has metastasized, that is, spread to other distant organs, the five-year overall survival is less than 5%.
Cancer occurs when normal cells undergo a transformation that causes them to grow abnormally and multiply without control and potentially spread to other parts of the body. The cells form a mass or tumor that differs from the surrounding tissues from which it arises. Cancers are also called malignant tumors. Such tumors are dangerous because they take oxygen, nutrients, and space from healthy cells and because they invade and destroy or reduce the ability of normal tissues to function.
Most lung tumors are malignant. This means that they invade and destroy the healthy tissues around them and can spread throughout the body. The lung is a bad place for a cancer to arise because it contains a very rich network of both blood vessels and lymphatic channels through which cancer cells can spread.
- The tumors can spread to nearby lymph nodes or through the bloodstream to other organs. This process of spread is called metastasis.
- When lung cancer metastasizes, the tumor in the lung is called the primary tumor, and the tumors in other parts of the body are called secondary or metastatic tumors.
Some tumors in the lung are metastatic from cancers elsewhere in the body. The lungs are a common site for metastasis. If this is the case, the cancer is not considered to be lung cancer. For example, if prostate cancer spreads via the bloodstream to the lungs, it is metastatic prostate cancer (a secondary cancer) in the lung and is not called lung cancer.
Lung cancer comprises a group of different types of tumors. Lung cancers usually are divided into two main groups that account for about 95% of all cases.
- The division into groups is based on the type of cells that make up the cancer.
- The two main types of lung cancer are characterized by the cell size and cell type of the tumor when viewed under the microscope. They are called small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC includes several subtypes of tumors.
- SCLCs are less common, but they grow more quickly and are more likely to metastasize than NSCLCs. Often, SCLCs have already spread to other parts of the body when the cancer is diagnosed.
- About 5% of lung cancers are of rare cell types, including carcinoid tumor, lymphoma, and others.
The specific types of primary lung cancers are as follows:
- Adenocarcinoma (an NSCLC) is the most common type of lung cancer, making up 30% to 40% of all cases. A subtype of adenocarcinoma is called bronchoalveolar cell carcinoma, which creates a pneumonia-like appearance on chest X-rays.
- Squamous cell carcinoma (an NSCLC) is the second most common type of lung cancer, making up about 30% of all cases.
- Large cell cancer (another NSCLC) makes up 10% of all cases.
- SCLC makes up 20% of all cases.
- Carcinoid tumors account for 1% of all cases.