by Emily Goebel, MD FRCPC
January 12, 2023
Extramammary Paget disease of the vulva is a non-invasive type of vulvar cancer. The tumour starts from cells found in the skin on the surface of the vulva. It is important to distinguish this condition from secondary Paget disease which is the spread of tumour cells from the rectum, bladder, or cervix to the vulva.
Common symptoms of extramammary Paget disease include red, itchy skin. The changes in the skin may resemble eczema.
At the present time, we do not know what causes extramammary Paget disease of the vulva.
When extramammary Paget disease starts in the vulva, it is considered a type of non-invasive cancer. This means that the tumour cells are unable to spread to other parts of the body. In contrast, secondary Paget disease is a type of cancer that has spread to the vulva from a tumour located in the rectum, bladder, or cervix.
The diagnosis of extramammary Paget disease of the vulva is usually made after a small sample of tissue is removed in a procedure called a biopsy. The entire tumour will usually be removed fully in a larger surgical procedure called an excision or vulvectomy.
When examined under the microscope, the tumour is made up of large, round, abnormal-looking cells. The cytoplasm (body of the cell) is light pink and the nucleus (the part of the cell that holds the genetic material) is large. The tumour cells are found in a layer of skin called the epidermis.
Your pathologist may perform a test called immunohistochemistry to confirm the diagnosis and to exclude other cancers that may look similar to extramammary Paget disease. The tumour cells will be positive or reactive for immunohistochemical markers such as CK7 and GCDFP-15 and negative or non-reactive for p63 and S100, which you may see included in your pathology report.
Extramammary Paget disease starts from cells normally found on the surface of the vulva called the epidermis. As the tumour grows, the cells usually stay in the epidermis. However, over time, tumour cells can spread into the layers of tissue below the epidermis, specifically the dermis or subcutaneous tissue. Pathologists use the term invasion to the spread of tumour cells into these layers of tissue. Tumours that show deep invasion into the dermis or subcutaneous tissue are more likely to spread to lymph nodes or other parts of the body.
A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. A negative margin means that no cancer cells were seen at the cut edge of the tissue. In contrast, a positive margin means that cancer cells were seen at the cut edge of the tissue. A positive margin increases the risk that the tumour will grow back in that location.