by Jason Wasserman MD PhD FRCPC
May 30, 2023

What is Bowen’s disease?

Bowen’s disease is an early non-invasive type of skin cancer. The tumour starts from the cells normally found in a part of the skin called the epidermis. Another name for Bowen’s disease is squamous cell carcinoma in situ. If left untreated, Bowen’s disease can change into a type of invasive cancer called squamous cell carcinoma.

Where in the skin does Bowen’s disease start?

Bowen’s disease starts from squamous cells normally found in the outermost layer of skin called the epidermis. Over time, the tumour cells replace the normal, healthy squamous cells. Bowen’s disease is called non-invasive because the tumour cells have not spread into any of the other layers of skin.

What are the symptoms of Bowen’s disease?

Bowen’s disease typically presents as a slow-growing, red, scaly area of skin.

What causes Bowen’s disease?

The most common cause of Bowen’s disease is long-term and excessive exposure to UV radiation, typically from the sun but other sources such as tanning beds are also implicated. Immune suppression as a result of medications or immune dysfunction increases the risk of developing Bowen’s disease.

Where on the body is Bowen’s disease normally found?

Bowen’s disease typically involves sun-exposed areas of the body, specifically the face, neck, lower legs, and hands.

Is Bowen’s disease benign or malignant?

Bowen’s disease is made up of malignant cells, however, because the tumour is non-invasive, the cells are unable to spread to other parts of the body. For this reason, treated early, Bowen’s disease behaves like a benign disease.

Can the tumour cells in Bowen’s disease spread to other parts of the body?

No. Bowen’s disease is a non-invasive type of cancer which means the tumour cells are unable to spread to other parts of the body.

How is the diagnosis of Bowen’s disease made?

The diagnosis is usually made after a small tissue sample is removed in a biopsy procedure. The diagnosis can also be made after the entire tumour is removed in a procedure called an excision. If the diagnosis is made after a biopsy, your doctor will probably recommend a second surgical procedure to remove the rest of the tumour.

What does Bowen’s disease look like under a microscope?

When examined under the microscope, the tumour cells in Bowen’s disease are larger and darker than the squamous cells normally found in the epidermis of the skin. Pathologists often describe these abnormal-looking squamous cells as atypical or pleomorphic. In order to make the diagnosis of Bowen’s disease, the tumour cells should only be seen in the epidermis.

What is a margin and why are margins important?

In pathology, a margin is the edge of a tissue that is cut when removing a tumour from the body. The margins described in a pathology report are very important because they tell you if the entire tumour was removed or if some of the tumour was left behind. The margin status will determine what (if any) additional treatment you may require.

Most pathology reports only describe margins after a surgical procedure called an excision or resection has been performed for the purpose of removing the entire tumour. For this reason, margins are not usually described after a procedure called a biopsy is performed for the purpose of removing only part of the tumour. The number of margins described in a pathology report depends on the types of tissues removed and the location of the tumour. The size of the margin (the amount of normal tissue between the tumour and the cut edge) depends on the type of tumour being removed and the location of the tumour.

Pathologists carefully examine the margins to look for tumour cells at the cut edge of the tissue. If tumour cells are seen at the cut edge of the tissue, the margin will be described as positive. If no tumour cells are seen at the cut edge of the tissue, a margin will be described as negative. Even if all of the margins are negative, some pathology reports will also provide a measurement of the closest tumour cells to the cut edge of the tissue.

A positive (or very close) margin is important because it means that tumour cells may have been left behind in your body when the tumour was surgically removed. For this reason, patients who have a positive margin may be offered another surgery to remove the rest of the tumour or radiation therapy to the area of the body with the positive margin.

What does it mean if my report says the tumour was incompletely excised?

Incompletely excised means that only part of the tumour was removed from the body. Pathologists describe a tumour as being incompletely excised when tumour cells are seen at the edge of the tissue. In pathology, the cut edge of the tissue is also called the margin. It is normal for a tumour to be incompletely excised after a small procedure such as a biopsy because these procedures are usually not performed to remove the entire tumour. However, larger procedures such as excisions and resections are usually performed to remove the entire tumour. If a tumour is incompletely excised, your doctor may recommend another procedure to remove the rest of the tumour.