Squamous cell carcinoma
This article was last reviewed and updated on April 9, 2019
by Jason Wasserman, MD PhD FRCPC
Squamous cell carcinoma is a type of cancer of the esophagus.
It starts from the cells that line the inside of the esophagus.
Your pathology report for squamous cell carcinoma includes important information such as the tumour size and the distance the cancer cells have traveled into the wall of the esophagus and surrounding tissues.
The esophagus is a long hollow tube that starts at the back of your throat and ends at the top of your stomach. Swallowed food travels down the esophagus into the stomach.
The inside of the normal esophagus is lined by specialized cells called squamous cells which form a barrier called the epithelium. Squamous cell carcinoma is a type of cancer (a malignant tumour) that develops from the squamous cells in the epithelium.
Squamous cell carcinoma is associated with both long term alcohol use and smoking although a variety of injuries and chemicals can also cause squamous cell carcinoma in the esophagus.
Symptoms of squamous cell carcinoma in the esophagus include difficultly or pain when swallowing food. The symptoms are worse initially with solids but progress to both solids and liquids.
The diagnosis of squamous cell carcinoma is usually made after a small sample of tissue is removed in a procedure called a biopsy and the tumour is later removed in a resection specimen such as an esophagectomy.
Pathologists use the word grade to describe how different the cancer cells in squamous cell carcinoma look compared the squamous cells normally found in the esophagus.
Pathologists divide the grade into three categories based on how the cancer cells look when examined under the microscope.
Well differentiated - The cancer cells look very similar to the normal squamous cells.
Moderately differentiated - The cancer cells are clearly abnormal but still share many features with normal squamous cells.
Poorly differentiated - The cancer cells look very different than normal squamous cells. Special tests such as immunohistochemistry may need to be performed to prove that the cancer cells are squamous cells.
Why is this important? Grade is important because poorly differentiated tumours are associated with worse prognosis.
The esophagus is a long tube that starts at the back of your throat and ends at the top of the stomach. The normal esophagus is divided into three parts:
Cervical esophagus - This is the first part of the esophagus. It starts at the back of the throat and ends near the bottom of your neck.
Thoracic esophagus - This is the second part of the esophagus. It starts at the bottom of your neck and ends where the esophagus meets the stomach.
Gastroesophageal junction - This is the connection between the esophagus and the stomach.
In your report, tumour site refers to the part of the esophagus or stomach involved by the tumour. Most squamous cell carcinomas start in the cervical or thoracic part of the esophagus.
This is the size of the tumour. Tumour size will only be described in your report after the entire tumour has been removed. The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 4.0 cm by 2.0 cm by 1.5 cm, your report will describe the tumour as being 4.0 cm.
The esophagus is a tube and the wall of the tube is made up of different layers of tissue. All squamous cell carcinomas start in the epithelium on the inner surface of the esophagus. Tumour extension describes how far the cancer cells have traveled from the epithelium into the deeper layers of tissue or the organs surrounding the esophagus. The movement of cancer cells from the epithelium into the tissue below is called invasion.
Your pathology report will describe the tumour extension as follows:
Lamina propria, muscularis mucosae, submucosa - These three layers of tissue are immediately below the epithelium. Once the cancer cells have broken out of the epithelium and entered this tissue, the diagnosis changes to squamous cell carcinoma.
Muscularis propria - The cancer cells have entered the thick bundle of muscle located in the middle of the wall.
Adventitia - The cancer cells have reached the outer surface of the esophagus. Once the cancer cells pass the adventitia they can invade nearby organs and tissues such as the bladder or abdominal wall.
Cancer cells that have traveled further into the wall of the esophagus or surrounding organs are more likely to come back after treatment in the area of the original tumour or travel (metastasize) to a distant site such as the lungs.
Why is this important? Tumour extension is important because it is used to determine the pathologic tumour stage (see Pathologic stage below).
Nerves are the long wires that carry information between your body and your brain. Cancer cells wrapped around a nerve is called perineural invasion.
Why is this important? Perineural invasion is important because cancer cells can travel along a nerve to tissues far away from the original tumour. Perineural invasion is associated with a higher risk that the tumour will recur at the same site or travel (metastasize) to a distant site such as the lungs after treatment.
Lymphatics and blood vessels are channels that normal cells use to travel around the body. The presence of cancer cells within a lymphatic or blood vessel is called lymphovascular invasion and is associated with a higher risk that the tumour will travel (metastasize) to a lymph node or a distant site such as the lungs.
In the esophagus, a margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. The types of margins present will depend on the type of procedure that was performed.
For esophagectomy specimens where an entire segment of esophagus has been removed, the margins will include:
Proximal margin - This margin is located near the upper portion of the esophagus closer to the mouth.
Distal margin - This margin is located near lower portion of the esophagus. The distal margin can be in the esophagus or the stomach.
Radial margin - This is the tissue around the outside of the esophagus.
For endoscopic resections where only a small piece of the inside of the esophagus has been removed, the margins will include:
Mucosal margin - This is the tissue that lines the inner surface of the esophagus.
Deep margin - This tissue is inside the wall of the esophagus. It is located below the tumour.
In the esophagus, a margin is considered positive when there are cancer cells at the very edge of the cut tissue.
Why is this important? A positive margin is associated with a higher risk that the tumour will recur in the same site after treatment.
If you received treatment (either chemotherapy or radiation therapy) for your cancer prior to the tumour being removed, your pathologist will examine all of the tissue submitted to see how much of the tumour is still alive (viable).
The treatment effect will be reported on a scale of 0 to 3 with 0 being no viable cancer cells (all the cancer cells are dead) and 3 being extensive residual cancer with no apparent regression of the tumour (all or most of the cancer cells are alive).
Lymph nodes with cancer cells will also be examined for treatment effect.
Metastatic disease describes the process where cancer cells escape the main tumour and travel to another part of the body. Lymph nodes are small immune organs located throughout the body. They are a common target for metastatic disease.
The presence of cancer cells in a lymph node (also called lymph node metastases) is associated with a higher risk that the cancer cells will be found in other lymph nodes or in a distant organ such as the lungs. For this reason, lymph nodes in the area of the tumour are often removed and submitted for pathological examination.
Most reports include the total number of lymph nodes examined and the number that contain cancer cells.
The pathologic stage for squamous cell carcinoma is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer.
This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M) to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means more advanced disease and worse prognosis.
Pathologic stage is not reported on a biopsy specimen. It is only reported when the entire tumour has been removed in an excision or resection specimen.
Tumour stage (pT) for squamous cell carcinoma of the esophagus
Squamous cell carcinoma is given a tumour stage between 1 and 4 based on the distance the cancer cells have traveled from the epithelium on the inner surface of the esophagus into the wall of the esophagus.
Tis - The cancer cells are still only in the epithelium on the inner surface of the esophagus. Another name for this type of tumour is high grade dysplasia.
T1 - The cancer cells have broken out of the epithelium and have entered the lamina propria, muscularis mucosae, or submucosa.
T2 - The cancer cells are in the muscularis propria of the esophagus.
T3 - The cancer cells have gone through the entire wall and is on the outer surface of the esophagus.
T4 - The tumour has gone into surrounding organs or tissues such as the lungs or aorta.
Nodal stage (pN) for squamous cell carcinoma of the esophagus
Squamous cell carcinoma is given a nodal stage between 0 and 3 based on the presence of cancer cells in a lymph node and the number of lymph nodes involved.
N0 - No cancer cells are seen in any of the lymph nodes examined.
N1 - Cancer cells are seen in one or two lymph nodes.
N2 - Cancer cells are seen in three to six lymph nodes.
N3 - Cancer cells are seen in more then six lymph nodes.
If no lymph nodes are submitted for pathological examination, the nodal stage cannot be determined and the nodal stage is listed as NX.
Metastatic stage (pM) for squamous cell carcinoma of the esophagus
Squamous cell carcinoma is given a metastatic stage between 0 and 1 based on the presence of cancer cells at a distant site in the body (for example the lungs). The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined and is listed as X.