by Jason Wasserman MD PhD FRCPC
May 13, 2022
Squamous cell carcinoma in situ (CIS) is a non-invasive type of laryngeal (throat) cancer. Squamous CIS starts from the cells that cover the inside surface of the larynx. Squamous CIS can start in any part of the larynx although the most common location is the vocal cord. If left untreated, squamous CIS is associated with a high risk of developing a type of laryngeal cancer called squamous cell carcinoma. Another name for squamous CIS is severe squamous dysplasia.
The most common cause of squamous CIS in the larynx is smoking. Other causes include excessive alcohol consumption, immune suppression, and prior radiation to the neck.
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 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. The diagnosis can also be made after the entire tumour is removed in a procedure called an excision or resection.
The diagnosis of squamous CIS 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 carcinoma in situ 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.
The abnormal cells in squamous CIS 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 CIS.
The microscopic appearance of squamous cell carcinoma in situ in the larynx.
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. Margins will only be described in your report after the entire tumour has been removed.
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.
Lymph nodes are small immune organs located throughout the body. Tumour cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour. The movement of tumour cells from the tumour to a lymph node is called metastasis.
Lymph nodes are not always removed for squamous carcinoma in situ. When lymph nodes are removed at the same time as the tumour, they are usually from the neck and the procedure is called a neck dissection.
The lymph nodes removed usually come from different areas of the neck and each area is called a level. The levels in the neck include 1, 2, 3, 4, and 5. Your pathology report will often describe how many lymph nodes were seen in each level sent for examination.
Lymph nodes on the same side as the tumour are called ipsilateral while those on the opposite side of the tumour are called contralateral.
Your pathologist will carefully examine each lymph node for tumour cells. Lymph nodes that contain tumour cells are often called positive while those that do not contain any tumour cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain tumour cells.
Because squamous carcinoma in situ is a non-invasive disease, it is very unlikely that cancer cells will be found in any of the lymph nodes examined.