This article was last reviewed and updated on October 31, 2018
by Emily Goebel, MD FRCPC
The normal vulva
The vulva is the external part of the female genital tract. It forms the opening of the vagina and includes the mons pubis, labia majora, labia minora and clitoris. The surface of the vulva is covered by skin. The outside layer of the skin is called the epidermis and is made up of specialized cells called squamous cells. The tissue beneath the epidermis is called the dermis, it contains blood vessels and connective tissue.
What is squamous cell carcinoma?
Squamous cell carcinoma is a type of cancer that develops in the vulva from the squamous cells in the epidermis.
In many cases, squamous cell carcinoma develops from one of two pre-cancerous diseases:
HSIL and dVIN are different from squamous cell carcinoma because in HSIL and dVIN the abnormal cells are seen only in the epidermis of the vulva. Squamous cell carcinoma occurs when there is movement of cancer cells from the epidermis into the dermis below. The movement of cancer cells into the dermis is called invasion.
The diagnosis of squamous cell carcinoma is usually made after a small tissue sample is removed in a procedure called a biopsy. The entire tumour is usually then removed in a procedure called an excision or resection.
Grade is a word pathologists use to describe how different cancer cells look compared to the normal squamous cells in the epidermis. The grade can only be determined after tissue has been examined under the microscope.
The grade is usually divided into three levels of differentiation:
Why is this important? Grade is important because poorly differentiated tumours tend to behave more aggressively than well differentiated tumours.
After the entire tumour has been removed, your pathologist will measure it in three dimensions and the largest dimension will be described in your pathology report.
Depth of invasion is determined by measuring the tumor from the bottom of the epidermis on the surface of the vulva to the cancer cells at the very deepest point of invasion.
Why is this important? The size of the tumour and depth of invasion are important because they are used to determine the tumour stage (see Pathologic stage below).
Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through lymphatic channels.
Cancer cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of cancer cells from the tumour to another part of the body is called metastasis.
Before cancer cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.
Why is this important? Lymphovascular invasion increases the risk that cancer cells will be found in a lymph node or a distant part of the body such as the lungs.
A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. A margin is considered positive when the cancer cells are seen at the edge of the cut tissue. If HSIL or dVIN are seen at the margin that will also be described in your report.
Why is this important? Finding cancer cells at the margin increases the risk that the tumour will grow back in that location.
Lymph nodes are small immune organs located throughout the body. Cancer cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of cancer cells from the tumour to a lymph node is called a metastasis.
Most reports include the total number of lymph nodes examined and the number, if any, that contain cancer cells.
Your pathologist will carefully examine all lymph nodes for cancer cells. Lymph nodes that contain cancer cells are often called positive while those that do not contain any cancer cells are called negative.
Isolated tumour cells
Isolated tumour cells are a group of a cancer cells found in a lymph node that measure less than 0.2 millimeter in size.
Why is this important? Finding cancer cells in a lymph node 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. The risk is less if only isolated tumour cells were found.
Pathologic stage (pTNM)
The pathologic stage for squamous cell carcinoma of the vulva 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.
Tumour stage (pT) for squamous cell carcinoma
Squamous cell carcinoma is given a tumour stage between 1 and 3. Your pathologist will look for three features in order to determine the tumour stage:
1. The size of the tumour.
2. Depth of invasion (see Tumour size above).
3. Tumor extension which is the spread of cancer cells into nearby tissues including the urethra, vagina, bladder or rectum..
Nodal stage (pN) for squamous cell carcinoma
Squamous cell carcinoma is given a nodal stage of 0 or 3 based on the number of lymph nodes involved by cancer and the size of the cancer in the lymph nodes.
If no cancer cells are seen in any of the lymph nodes examined, the nodal stage is N0. Lymph nodes with isolated tumour cells are also given an nodal stage of N0.
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
Squamous cell carcinoma is given an metastatic stage of 0 or 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 assigned 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 MX.