Squamous carcinoma in situ
This article was last reviewed and updated on November 10 2019.
by Jason Wasserman, MD PhD FRCPC
Squamous carcinoma in situ is a pre-cancerous condition that develops in the larynx.
Without treatment, squamous carcinoma in situ can turn into a type of cancer called squamous cell carcinoma.
The larynx includes the vocal cords, aryepiglottic folds, arytenoids, ventricle, and commisures.
When we breathe, air travels from our mouth and nose to our lungs. On its way to the lungs, air passes through a part of the throat called the larynx. You cannot see your larynx because it starts at the very back of the tongue.
Most of the larynx is a hollow tube filled with air. The larynx helps us breathe and create sound when we talk.
The larynx is divided into three sections from top to bottom and each section is made up of smaller parts. Most pathology reports will describe the sections or parts of the larynx examined.
Supraglottis - The supraglottis is the first section of the larynx. The supraglottis includes the following smaller parts:
False vocal cords.
Glottis - The glottis is the second section and it is in the middle of the larynx. The glottis includes the following smaller parts:
True vocal cords.
Subglottis- The subglottis is the third and last section of the larynx. It has no smaller parts.
The inner surface of the larynx is lined by cells called squamous cells. These cells form a barrier on the surface of the larynx called the epithelium. The tissue below the epithelium is called stroma.
What is squamous carcinoma in situ?
Squamous carcinoma in situ is a pre-cancerous disease that starts from the squamous cells on the inside surface of the larynx. Squamous carcinoma in situ a is called a pre-cancerous disease because it can turn into a type of invasive cancer called squamous cell carcinoma.
Other names for this disease are severe keratinizing squamous dysplasia and high grade dysplasia.
When examined under a microscope, the abnormal squamous cells in squamous carcinoma in situ are only found in the epithelium on the surface of the larynx. Compared to normal, healthy cells, the cells in squamous carcinoma in situ look very abnormal when examined under the microscope. They are larger and darker (hyperchromatic) and appear disorganized compared to normal cells.
In order to become squamous cell carcinoma, the abnormal cells in squamous carcinoma in situ have to spread from the epithelium into the stroma below. The movement of abnormal cells from the epithelium into the stroma below is called invasion.
What causes squamous carcinoma in situ?
Smoking and high levels of alcohol consumption increase the risk for developing both squamous carcinoma in situ and squamous cell carcinoma.
How do pathologists make this diagnosis?
The diagnosis of squamous carcinoma in situ is usually made after a small sample of tissue is removed in a procedure called a biopsy. The tissue is then sent to a pathologist for examination under a microscope.
Treatment for squamous carcinoma in situ
Because the risk of developing squamous cell carcinoma is high, most patients diagnosed with squamous carcinoma in situ are offered treatment.
Treatment options for this condition include surgery to remove the diseased tissue and radiation. The type of surgery offered and the amount of tissue removed will depend on the part of the larynx involved and the size of the area with disease.
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 margin is considered positive when squamous carcinoma in situ is seen at the very edge of the cut tissue.
A negative margin means that squamous carcinoma in situ 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.
Why is this important? A positive margin is associated with a higher risk that the disease will come back (recur) in the same site after treatment.