Squamous dysplasia of the larynx

by Jason Wasserman MD PhD FRCPC
April 25, 2023

What is squamous dysplasia of the larynx?

Squamous dysplasia in the larynx is a precancerous disease. It develops from the squamous cells that cover the inner surface of the larynx. The larynx is a part of the throat that includes the vocal cords. Squamous dysplasia is considered a precancerous disease because it can over time turn into a type of laryngeal cancer called squamous cell carcinoma.

Where does squamous dysplasia in the larynx start?

Squamous dysplasia in the larynx starts from squamous cells normally found in a thin layer of tissue called the epithelium. The epithelium covers the inside surface of the larynx.

What causes squamous dysplasia in the larynx?

The most common cause of squamous dysplasia in the larynx is smoking. Other causes include excessive alcohol consumption, immune suppression, and prior radiation to the neck.

Is squamous dysplasia in the larynx a type of cancer?

No. Squamous dysplasia in the larynx is not cancer. It is, however, a precancerous condition that can turn into a type of laryngeal cancer called squamous cell carcinoma over time.

How do pathologists make the diagnosis of squamous dysplasia in the larynx?

The diagnosis of squamous dysplasia is usually made after a small sample of tissue is removed in a procedure called a biopsy. The biopsy is usually performed because your doctor saw an abnormal-looking area of tissue during an examination of your larynx. Your pathology report will probably say what part of the larynx was sampled in the biopsy.

How is the diagnosis of squamous dysplasia in the larynx made?

The diagnosis of squamous dysplasia in the oral cavity is usually made after a small sample of tissue is removed in a procedure called a biopsy. The biopsy is usually performed because you or your doctor saw an abnormal-looking area of tissue when your larynx was examined. Your pathology report will probably say what part of the larynx was sampled in the biopsy (for example, the vocal cords). The diagnosis can also be made after a larger piece of tissue is removed in a procedure called an excision.

What does squamous dysplasia in the larynx look like under the microscope?

Compared to normal, healthy squamous cells, the abnormal squamous cells in an area of squamous dysplasia are larger, darker, and disorganized. Pathologists use the word hyperchromatic to describe cells that look darker than normal cells. Large clumps of genetic material called nucleoli may also be seen in the nucleus of the abnormal cells. These squamous cells also commonly undergo an abnormal pattern of development which results in a process called keratinization.

What does it mean if squamous dysplasia is described as mild, moderate, or severe?

In the larynx, squamous dysplasia is commonly divided into three grades: mild squamous dysplasia, moderate squamous dysplasia, and severe squamous dysplasia.

The grade of squamous dysplasia is very important because it is related to the risk of developing a type of laryngeal cancer called squamous cell carcinoma in the future. Mild squamous dysplasia is associated with the lowest risk of developing cancer and those who do develop cancer tend to develop it after many years. Moderate and severe squamous dysplasia are associated with the highest risk of developing cancer and patients are typically offered treatment to remove the disease before it progresses to cancer.

Pathologists determine the grade by comparing the abnormal cells in the disease area to the healthy squamous cells normally found in the larynx. Specifically, pathologists look at the size, shape, and colour of the abnormal squamous cells and the number of mitotic figures (dividing cells).

What is a margin?

A margin is any healthy tissue that was cut by the surgeon in order to remove the abnormal area of tissue from your body. Whenever possible, surgeons will try to cut healthy tissue well outside of the abnormal area to reduce the risk that any abnormal cells will be left behind after the tissue is removed.

Your pathologist will carefully examine all the margins in your tissue sample to see how close the abnormal cells are to the edge of the cut tissue. Margins will only be described in your report after the entire abnormal area of tissue has been removed. Margins are not described in a report after a biopsy has been performed.

A negative margin means that squamous dysplasia was not seen at the very edge of the cut tissue. If all the margins are negative, most pathology reports will say how far the closest abnormal cells were to the cut edge of the tissue. The distance is usually described in millimeters.

A margin is considered positive when squamous dysplasia is seen at the very edge of the cut tissue. A positive margin is associated with a higher risk that the disease will come back (recur) in the same site after treatment.