Squamous carcinoma in situ of the oral cavity

by Jason Wasserman MD PhD FRCPC
June 16, 2022

About this article: This article was created by doctors to help you read and understand your pathology report for squamous carcinoma in situ (CIS) in the oral cavity. If you have any questions about this article or your pathology report, please contact us.

What is squamous carcinoma in situ (CIS)?

Squamous carcinoma in situ (CIS) is a pre-cancerous disease involving the tissue on the surface of the oral cavity. This area includes the lips, tongue, floor of mouth, cheeks, and hard palate. Squamous CIS is considered a pre-cancerous disease because it can over time turn into a type of laryngeal cancer called squamous cell carcinoma. Another name for squamous CIS is severe keratinizing squamous dysplasia.

What causes squamous carcinoma in situ in the oral cavity?

The most common cause of squamous CIS in the oral cavity is smoking. Other causes include excessive alcohol consumption, immune suppression, and inflammatory conditions such as lichen planus.

How is the diagnosis of squamous carcinoma in situ in the oral cavity made?

The diagnosis of squamous CIS 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 within your oral cavity. Your pathology report will probably say what part of the oral cavity was sampled in the biopsy. The diagnosis can also be made after a larger piece of tissue is removed in a procedure called an excision.

What does squamous carcinoma in situ look like under the microscope?

Squamous CIS starts from specialized squamous cells in a thin layer of tissue called the epithelium. When examined under the microscope, the abnormal cells in an area of squamous CIS are usually larger than normal, healthy squamous cells. The cells may be described as hyperchromatic as the nucleus (the part of the cell that holds the genetic material) is often darker than normal. Large clumps of genetic material called nucleoli may also be seen in the nucleus of the abnormal cells. These squamous cells also undergo an abnormal pattern of development which results in a process called keratinization.

What is a margin?

A margin is any tissue that was cut by the surgeon in order to remove the area of squamous CIS from your body. The types of margins described in your report will depend on the area of the oral cavity involved and the type of surgery performed. Margins will only be described in your report after the entire abnormal area of tissue has been removed.

A negative margin means that squamous CIS was not seen at any of the cut edges of tissue. A margin is called positive when there is squamous CIS at the very edge of the cut tissue. A positive margin is associated with a higher risk that squamous carcinoma in situ or squamous cell carcinoma will come back at the same site after treatment.