Only cancers that begin in the lungs are called "lung cancer." Sometimes cancer from other parts of the body may spread to the lungs, but when that happens, it is not called lung cancer. For example, breast cancer that spreads to the lungs is still breast cancer, and will be treated as breast cancer, not lung cancer. Lung cancer that spreads to the liver is treated as lung cancer, not liver cancer.

A cancer forms when cells start to multiply out of control. All of the normal cells in your body have very specific jobs and functions. For example, intestine cells absorb vitamins, minerals and other nutrients from our food; red blood cells carry oxygen throughout the body; and white blood cells fight infections. Normal cells stop growing and dividing when they get old. Normal cells also die if they are injured.

Cancer cells are different. They do not function normally and they often divide uncontrollably. Cancer cells do not die when they grow old. They may spread to nearby organs. They also can spread through the blood stream, invade nearby lymph nodes and metastasize. Common lung cancer metastasis sites include the brain, bones and liver.

Why does cancer happen?
How does cancer spread?
Types of lung cancer
What is staging, and why is it important?
How will doctors know the stage of my cancer?

Why does cancer happen?

Every cell contains genes. Genes are the “brains” that tell the cell what to do. When the cell’s genes are mutated, cancer may result. Some of these changes are inherited – they are passed down from parent to child; others may be due to things you are exposed to, such as cigarette smoke, radon and asbestos. These mutations to the genes can cause cells to multiply uncontrollably, resulting in a mass of tissue called a tumor.

How does cancer spread?

Lung cancer can spread to other organs in one of three ways:

1. The cancer tumor grows and invades another organ near the lungs.
2. Cancer cells travel through the blood stream.
3. Cancer cells travel through the lymphatic system.

The lymphatic system includes tissues and organs that produce, store and carry white blood cells that fight infection and disease. It includes the bone marrow, spleen, thymus, and lymph nodes.

There are hundreds of lymph nodes scattered throughout the body and they are important because cancer sometimes can spread through the lymphatic system. Cancer cells traveling through the body in lymph fluid can be trapped in the lymph nodes.

If you have surgery for your cancer, the surgeon also will likely remove some lymph nodes at the time of the operation. If the lymph nodes contain cancer, it raises the question of whether the cancer also may have escaped out of the lymph nodes and spread elsewhere in your body.

The most important lymph nodes involved with lung cancer are called hilar lymph nodes, which are located near the tumor (also called N1 nodes). Mediastinal lymph nodes are nodes between the lung and the heart. If they are on the same side as the tumor, they are called N2 nodes. If they are on the opposite side of the chest, they are called N3 nodes.

The most common sites where lung cancer spreads are:
  • Elsewhere in the lungs
  • The liver
  • The adrenal glands
  • The bones
  • The brain

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Types of lung cancer

There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). There are several subtypes of NSCLC. The most common are:
  •Adenocarcinoma
  •Squamous cell carcinoma
  •Large cell carcinoma
If you have NSCLC, it is important to know the subtype because it will help your medical team develop the right treatment plan for you. The majority of lung cancers (about eight out of ten) are NSCLC.

Small cell lung cancers tend to grow and spread more rapidly and cause symptoms sooner than non-small cell cancers. For these reasons, surgery usually is not a good option for small cell lung cancers, and treatment is more likely to be with chemotherapy.

There are many other types of cancers that occur in the chest, most of which are rare. One of these, mesothelioma, is commonly associated with exposure to asbestos.

Bronchioloalveolar Carcinoma (BAC) is a rare form of adenocarcinoma. The number of cases of BAC is rising worldwide. BAC spreads throughout the lung, unlike more typical cancer cells, which tend to “stick together” and form solid, individual tumors. The cause of BAC is not known. Although people who smoke can get BAC, it often occurs in people who have never smoked. Click here to view a podcast on the basics of BAC.

What is staging, and why is it important?

When you are diagnosed with lung cancer, your doctor will determine the type of lung cancer you have and the stage of the disease. Staging is based on the tumor’s location and size and whether it has spread to any lymph nodes in the area or to other organs. It is important to know what stage of cancer you have because the type and stage of the cancer will help your medical team determine which treatment plan is right for you. NSCLC is staged as I, II, III, or IV, while SCLC is usually classified as limited or extensive stage.

Non-Small Cell Lung Cancer (NSCLC)
Stage I
A tumor that has not spread to any lymph nodes or other organs and is up to 5 cm wide is classified as Stage I. This tumor is typically resectable. Stage IA cancers are 3 cm or smaller, and stage IB cancers are between 3 and 5 cm.

Stage II
A tumor that is up to 5 cm wide and has spread to lymph nodes on the same side of the chest, or a tumor that is 5-7 cm but has not spread to any lymph nodes is stage IIA. Tumors that have not spread to any lymph nodes but are larger than 7 cm, have begun to invade structures within the chest, or have another tumor in the same lobe of the lung are stage IIB. Tumors that are 5-7 cm and have spread to lymph nodes on the same side of the chest are also stage IIB. Generally, these tumors can be removed surgically.

Stage III
A tumor that does not appear to have spread to other organs beyond lymph nodes in the chest is classified as Stage III. Often, Stage III tumors are unresectable. Stage IIIA tumors have spread to lymph nodes in the center of the chest. Stage IIIB tumors have spread to lymph nodes on the opposite side of the chest or involve major structures, such as the heart or arteries.

Stage IV
Cancer that is accompanied by pleural effusion or that has metastasized to other parts of the body is called stage IV. Although stage IV cancers are quite difficult to cure, there are treatments available that may help you live longer.

Small Cell Lung Cancer (SCLC)
Limited Stage SCLC is a cancer that is limited to the chest such that radiation can be used to treat it, in addition to chemotherapy.

Extensive Stage SCLC is cancer that has spread to other areas of the chest or other parts of the body. Although it is rarely cured, this type of cancer often responds well to chemotherapy and patients experience a great improvement in symptoms.

How will a doctor know the stage of my cancer?

Doctors will determine stage by using any combination of the following procedures:

Computed tomography (CT) scans are sophisticated X-rays that show the locations and size of the tumor.

Positron emission tomography (PET) is based upon the fact that cancer cells are growing faster than normal cells, and thus consume more sugar. A small amount of special imaging medicine containing sugar is injected into a vein, and a machine is used to see where the sugar builds up. PET scans can help determine where tumors are in the body.

Bronchoscopy is a procedure in which a doctor puts a camera down the airway to see any tumors and possibly performs a biopsy using a needle.

Endobronchial ultrasound (EBUS) is a newer, more specialized type of bronchoscopy that uses sound waves to create an image of the tumor and nearby tissues to help the doctor decided what to biopsy.

Bone scans create pictures of the bones. A special imaging medicine is injected into a vein, and a specialized camera is used to see how healthy the bones are and weather there are any tumors in them.

Magnetic resonance imaging (MRI) uses magnetic fields to product detailed images of the body. MRI is particularly useful for finding abnormal growths in the brain.

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This information is not designed to be a substitute for medical advice provided by your treatment team.

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