By Jason Wasserman MD PhD FRCPC
February 7, 2023
Squamous cell carcinoma in situ (CIS) is a non-invasive type of throat cancer. If left untreated, squamous cell CIS is associated with a high risk of developing invasive squamous cell carcinoma. Other names for this condition include severe squamous dysplasia and high grade dysplasia.
Squamous cell CIS starts from specialized squamous cells that cover the inside surface of the larynx. Squamous cell CIS can start anywhere in the larynx although the most common site is the glottis which includes the vocal cords. Less common sites include the supraglottis and subglottis.
Squamous cell CIS of the larynx is called non-invasive because the tumour cells are located entirely within a thin layer of tissue on the inside surface of the larynx called the epithelium. This is the same location where healthy squamous cells are normally located. In contrast, a tumour is considered “invasive” if the tumour cells spread into the stroma below the epithelium.
Squamous cell CIS of the larynx is not considered malignant because the tumour cells are not able to spread to other parts of the body.
No. Because squamous cell CIS is non-invasive, the tumour cells are unable to spread to other parts of the body.
The most common cause of squamous cell CIS in the larynx is smoking. Other causes include excessive alcohol consumption, immune suppression, and prior radiation to the neck.
The diagnosis of squamous cell CIS 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.
When examined under the microscope, the cells in squamous cell CIS are larger and hyperchromatic (darker) than healthy squamous cells. Unlike healthy squamous cells, the tumour cells also appear disorganized. Large clumps of genetic material called nucleoli may also be seen in the nucleus of the abnormal cells.
This image shows an example of squamous cell carcinoma in situ viewed under the microscope.
A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. Whenever possible, surgeons will try to cut tissue outside of the tumour to reduce the risk that any cancer cells will be left behind after the tumour is removed. Your pathologist will carefully examine all the margins in your tissue sample to see how close the tumour cells are to the edge of the cut tissue.
A negative margin means there were no tumour cells at the very edge of the cut tissue. A margin is considered positive when there are tumour cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will come back (recur) in the same site after treatment. Margins will only be described in your report after the entire tumour has been removed.