Doctors use stages to describe the growth and spread of cancers. Stage 4, or IV, oral cancer means cancer has spread to a nearby lymph node or another part of the body.

Cancers happen when cells start to multiply uncontrollably, forming tumors. Oral cancer refers to cancers that originate:

  • on or under the tongue
  • on the inside of the mouth
  • on the gums
  • on the lips

Cancer can start anywhere in the body and spread to other parts. Doctors call the original tumor the primary tumor. If the cancer has spread to another part of the body, they call it metastatic cancer.

Around 53,000 people develop oral cancer in the United States every year. It accounts for about 3% of all cancer diagnoses.

This article will describe what stage IV oral cancer is and explain the condition’s different stages. It will also look at causes, treatments, and prevention.

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Doctors classify, or stage, cancers according to the size and location of the tumor and how far it has spread.

For oral cancer, they typically use the TNM system:

  • T stands for tumor: This refers to the size and location of the primary tumor.
  • N stands for node: This refers to whether the cancer has spread to the nearby lymph nodes, which are small glands that form part of the immune system.
  • M stands for metastasis: This refers to whether the cancer has spread to other parts of the body.

Doctors will use various tests to stage a person’s oral cancer using the TNM system.

There are four main stages of oral cancer, many of which are broken down into subcategories:

Stage I

The tumor is no more than 2 centimeters (cm) in size and does not reach any more than 5 millimeters (mm) into the tissue. It has not spread to the lymph nodes or other parts of the body. Doctors may call it T1, N0, M0.

Stage II

Stage II refers to T2, N0, M0. It can mean the tumor is no more than 2 cm in size and reaches between 5 mm and 10 mm into the tissue. Or it may mean the tumor is larger than 2 cm and the depth of invasion into the tissue is 10mm or less.

At this stage, the cancer has not spread.

Stage III

There are two stage III descriptions:

  • T3, N0, M0: The tumor is larger than 4 cm, and the depth of invasion is more than 10 cm, but it has not spread.
  • T1, T2 or T3, plus N1, M0: The tumor is any size, but has not reached into other parts of the mouth. There is cancer in one lymph node, and the tumor is less than 3 cm. It has not spread to other parts of the body.

Stage IV

There are three stage IV subcategories:

Stage IV A

Stage IV A may mean:

  • T4a, N0 or 1, M0: The tumor has grown into other parts of the mouth. The cancer is in one or more lymph nodes.
  • T1 to T4a, N2, M0: The tumor may have grown into other parts of the mouth. It has spread to one or more lymph nodes, and the tumor is larger than 6 cm.

At this stage, it has not spread to other parts of the body.

Stage IV B

Stage IV B can mean:

  • Any T, N3, M0: The primary tumor is any size. There is a tumor of 6 cm or more in a lymph node.
  • T4b, any N, M0: The cancer has grown into the muscles and bones around the mouth or at the base of the skull. It may be in a lymph node.

At stage IV B, the cancer has not spread to any other parts of the body.

Stage IV C

Stage IV C oral cancer has spread to another part of the body. It refers to cancers with any T, any N, and M1 according to the TNM system.

The American Cancer Society says most oral cancers are squamous cell carcinoma. That means it starts in the squamous cells in the lining of the mouth.

Other, less common, types of oral cancer are:

  • cancers that start in the salivary glands
  • lymphomas

Stage IV oral cancer treatment will depend on the subcategory:

Stage IV A

Surgeons will usually remove any affected lymph nodes. After that, people may receive radiotherapy, either on its own or with chemotherapy.

Stage IV B

Doctors may recommend surgery to remove the tumors. However, this is not always possible.

The person’s healthcare team may recommend a combination of surgery, radiotherapy, and chemotherapy.

Stage IV C

For stage IV C oral cancer, doctors may recommend chemotherapy on its own or immunotherapy.

They may also suggest radiation to help relieve symptoms.

Experts do not know what causes oral cancer. However, some things may make a person more likely to develop it. Doctors call these risk factors.

The risk factors for oral cancer include:

The outlook for people with oral cancer will depend on if and how far the cancer has spread at the time of diagnosis.

Overall 5-year survival rates can provide an estimated outlook. Survival rates indicate the average percentage of people alive 5 years after a diagnosis.

For oral cancer, the 5-year survival rate depends on the location of the cancer and whether it has spread to other parts of the body. For example, the 5-year survival rate for localized tongue cancer is about 83%.

People can reduce their risk of developing mouth cancer by:

  • avoiding smoking or chewing tobacco
  • limiting alcohol consumption
  • getting an HPV vaccination
  • eating plenty of fruit and vegetables
  • using lip balm with an SPF of at least 30 with both UVA and UVB protection
  • regularly going to the dentist

Doctors stage oral cancer according to the size of the tumor and whether it has spread to nearby lymph nodes or other parts of the body.

Stage IV oral cancer is cancer that starts in the mouth but has spread to nearby lymph nodes or another part of the body. The treatment and outlook will depend on the stage IV subcategory at diagnosis.