Floor of Mouth Cancer

The floor of mouth is a horseshoe-shaped area under the tongue, between the lower jaw bones (the mandible). When a malignant tumor grows in this area it is called floor of mouth cancer. The American Cancer Society estimates that 28,000 people in the United States develop oral or throat cancer each year and 7,000 die from it. Cancer of the floor of mouth accounts for 28-35% of all mouth cancers.


Cancer of the floor of mouth often looks like an ulcer and is painless. Sometimes people mistake this for a canker sore (aphthous ulcer). Often, by the time a patient sees a doctor for a diagnosis, the tumor has enlarged and grown into the neck.

Symptoms of floor of mouth cancer may include:

  • A sore in the mouth that continues to grow larger
  • Mouth pain
  • Dentures that no longer fit
  • White, red or dark patches inside the mouth
  • Difficulty moving the jaw
  • Jaw pain or swelling
  • Mouth becomes numb
  • Severe ear pain but the eardrum is normal
  • Lumps in the neck
  • Loose teeth or pain around the teeth
  • Painless ulcer or lump

Causes and Risk Factors

Men are diagnosed with floor of mouth cancer three to four times more often than women.

The most significant risk factors for floor of mouth cancer are tobacco and alcohol use. Smokeless tobacco (including snuff and betel nut) is more of a risk for this cancer than cigarettes because the plug of tobacco is pressed again the skin in the mouth.

Other potential causes include people with certain infections or decreased immunity, such as:

  • Exposure to the human papilloma virus (HPV), especially strains 16 and 18.
  • Organ transplant recipients
  • People with human immunodeficiency virus (HIV) disease


A doctor uses a tongue depressor to move the tongue and look at the floor of mouth. The inside of the mouth and cheeks are examined with a gloved finger to check the location and size of the tumor. Examination of the ears, nose, throat and neck are needed to help determine if the tumor has spread.

The doctor may also order tests including:

  • Blood tests
  • X-rays to determine if the tumor has spread to the lung
  • Fine Needle Aspiration Biopsy (FNA). A thin needle is placed in the mouth. The cells are aspirated (suctioned) and then examined under a microscope to determine if the lump is cancerous

Imaging studies to determine if the tumor has invaded nearby tissues or other organs of the body. These may include:

  • Orthopantomography (Panorex). This is a panoramic X-ray of the upper and lower jaw. It shows a view from ear-to-ear and helps determine if a tumor has grown into the jaw bone.
  • Computerized tomography (CT) scan. A computer is linked to an X-ray machine which creates a series of detailed pictures, with different angles, of areas inside the mouth and neck. A dye may be injected into a vein or a pill swallowed to help highlight the organs or tissue on the X-ray. This procedure may also be referred to as computerized axial tomography (CAT).
  • Magnetic resonance imaging (MRI). This machine uses a magnet, radio waves and a computer to create detailed pictures of the area inside the mouth and neck. This procedure may also be referred to as nuclear magnetic resonance imaging (NMRI).
  • Positron emission tomography (PET) scan. During a PET scan, a small amount of radioactive glucose (sugar) is injected into a vein. The scanner creates computerized pictures of the areas inside the body. Cancer cells absorb more radioactive glucose than normal cells so the tumor is highlighted on the pictures.


Early-stage floor of mouth cancer is often treated with surgery or radiation. Advanced cancer cases usually require a combination of surgery, radiation and chemotherapy.


Early-stage floor of the mouth cancer is often treated with surgery only. Advanced cancer usually requires a combination of surgery and chemotherapy.

To adequately remove a tumor from the floor of the mouth, 1 ½ cm (3/4 of an inch) of normal tissue should surround the tumor. The surgeon can remove all the tissue up to the bone if the tumor is not attached to bone. If the tumor is attached to the bone, the surgeon might need to remove a portion of the jaw bone. Reconstruction surgery can replace the part of the jaw that is removed.

If the lymph nodes in the neck are affected, a neck dissection may be needed to remove the nodes.


Medical oncologists administer chemotherapy if cancer has spread to lymph nodes or other organs. The medicine circulates in the blood and disrupts the growth of the cancer cells. Chemotherapy medications are taken by mouth or given through a vein over a period of several months.

Chemotherapy is not curative for this type of tumor, but when combined with surgery it is helpful in controlling the tumor. Chemotherapy is prescribed for different reasons:

  • After surgery to decrease the risk of the cancer returning
  • To slow the growth of a tumor and control symptoms when the cancer cannot be cured (palliative treatment)