Squamous Dysplasia of the Oral Cavity: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
February 24, 2026

Squamous dysplasia of the oral cavity is a precancerous condition that affects the lining of the mouth. It develops in squamous cells, which are flat cells that form the surface layer, also called the epithelium.

The oral cavity includes the lips, tongue, floor of the mouth, inner cheeks, gums, and hard palate. In squamous dysplasia, squamous cells begin to grow and mature abnormally. These cells may look irregular in size and shape, and may lose their normal, organized arrangement.

Squamous dysplasia is not cancer, but it is considered precancerous because the abnormal cells have the potential to develop into squamous cell carcinoma, the most common type of oral cavity cancer.

Where in the oral cavity does squamous dysplasia occur?

Squamous dysplasia can develop anywhere in the oral cavity that is lined by squamous epithelium. Common sites include the sides and underside of the tongue, the floor of the mouth, the inner lining of the cheeks, the gums, the hard palate, and the inner surface of the lips.

What causes squamous dysplasia of the oral cavity?

The most common cause of squamous dysplasia is tobacco use, including cigarettes, cigars, pipes, and smokeless tobacco. Tobacco exposes oral cavity cells to harmful chemicals that damage DNA and promote abnormal growth.

Heavy alcohol use also increases the risk, particularly when combined with tobacco. Alcohol can weaken the protective lining of the mouth and make it more vulnerable to injury.

Other contributing factors include immune suppression and chronic inflammatory conditions such as oral lichen planus. Long-standing irritation or inflammation can increase the likelihood that squamous cells will develop abnormal changes.

What symptoms can occur?

Many people with squamous dysplasia have no symptoms. The condition is often discovered after a dentist or doctor notices an abnormal area in the mouth.

When symptoms are present, they may include a persistent white patch, red patch, or mixed red and white area that does not heal. Some people experience tenderness, irritation, or sensitivity in the affected area.

How is this diagnosis made?

The diagnosis of squamous dysplasia is made after a biopsy, which is a small sample of tissue removed from the abnormal area. The tissue is examined under a microscope by a pathologist.

The pathologist evaluates the squamous cells to determine whether abnormal changes are present and, if so, how severe they are. The diagnosis may also be made after a larger piece of tissue is removed during a procedure called an excision.

Microscopic features

Under the microscope, squamous dysplasia shows changes in both the appearance of individual cells and the overall structure of the epithelium.

The abnormal squamous cells may have enlarged and darker nuclei. The nucleus is the part of the cell that contains genetic material. The cells may vary in size and shape and may appear crowded or overlapping. The normal orderly maturation of cells from the bottom to the surface of the epithelium may be disrupted.

Pathologists also look for an increased number of mitotic figures, cells actively dividing. An increased number of dividing cells can indicate abnormal growth.

How is squamous dysplasia graded?

In the oral cavity, squamous dysplasia is commonly divided into three grades: mild, moderate, and severe. The grade is based on how abnormal the cells appear and how much of the epithelial thickness is involved.

In mild squamous dysplasia, abnormal changes are limited to the lower third of the epithelium. The upper layers still show normal maturation. Mild dysplasia carries the lowest risk of progression to cancer, although monitoring is still important.

In moderate squamous dysplasia, abnormal cells extend into the middle third of the epithelium. The risk of progression is higher than with mild dysplasia.

In severe squamous dysplasia, abnormal cells involve more than two-thirds of the epithelial thickness. The cells appear more disorganized, and normal maturation is largely lost. Severe dysplasia carries the highest risk of progression to squamous cell carcinoma and is often treated by removing the affected area.

The grade reported in your pathology report helps guide management and follow-up.

What is the risk of developing oral cancer?

The risk of progression to squamous cell carcinoma depends on the grade of dysplasia and whether risk factors such as tobacco use continue.

Mild dysplasia has a lower risk of progression and may remain stable for many years. Moderate and severe dysplasia have a higher risk of developing into cancer, which is why treatment or closer monitoring is often recommended.

Early detection and appropriate management significantly reduce the risk of invasive cancer.

What is a margin, and why are margins important?

A margin is the edge of the tissue removed during surgery or excision. After the abnormal area is removed, the pathologist examines the margins under the microscope to see whether dysplasia extends to the cut edge.

A negative margin means that no dysplasia is seen at the edge of the tissue. This suggests that the abnormal area was completely removed.

A positive margin means that dysplasia is present at the edge of the tissue. This increases the risk that dysplasia may recur at the same site and may lead your doctor to recommend additional treatment or closer follow-up.

Questions you may want to ask your doctor

• What grade of squamous dysplasia was found in my biopsy?

• What is my risk of developing oral cancer?

• Should the area be removed or monitored?

• How often should I have follow-up examinations?

• Are there lifestyle changes that could reduce my risk?