Squamous dysplasia of the larynx

by Jason Wasserman MD PhD FRCPC
May 13, 2022

What is squamous dysplasia of the larynx?

Squamous dysplasia in the larynx is a pre-cancerous disease. It develops from the squamous cells that cover the inner surface of the larynx. Squamous dysplasia is considered a pre-cancerous disease because it can over time turn into a type of laryngeal cancer called squamous cell carcinoma.  Pathologists divide squamous dysplasia into three grades – mild, moderate, and severe – and the risk for developing cancer is highest with severe squamous dysplasia.

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.

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.

What does squamous dysplasia look like under the microscope?

The diagnosis of squamous dysplasia can only be made after a tissue sample is examined under the microscope. Compared to normal, healthy squamous cells, the abnormal 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.

The abnormal cells in squamous dysplasia are only seen in the epithelium. This is different from squamous cell carcinoma where the abnormal cells are also seen in the stroma below the epithelium. The movement of abnormal cells from the epithelium into the stroma is called invasion. Your pathologist will carefully examine your tissue sample to make sure there is no evidence of invasion before making the diagnosis of squamous dysplasia.

How do pathologists grade squamous dysplasia in the larynx?

Pathologists divide squamous dysplasia in the larynx into three levels or grades called mild, moderate, and severe. Pathologists determine the grade by comparing the abnormal squamous cells to normal, healthy squamous cells in the larynx. Another name for mild squamous dysplasia is low-grade dysplasia while moderate and severe squamous dysplasia are grouped together and called high-grade dysplasia.

The grade of dysplasia in the larynx is very important because it is related to the risk of developing cancer in the future. Mild (low-grade) dysplasia has a low risk of turning into cancer and is often left untreated. Moderate and severe (high-grade) dysplasia is associated with a much higher risk of progressing to cancer and patients with this condition are usually offered treatment to remove the diseased tissue.

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.

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