The information in this section has been gathered from existing peer-reviewed and other literature and has been reviewed by expert dermatologists on the CSPA Medical Advisory Board.

Skin cancer results from cells that multiply out of control. As a result, tumours, lumps, or masses can sometimes form on normal skin, and can be either benign (non-cancerous) or malignant (cancerous). Skin cancers are generally categorized as non-melanoma skin cancers (basal cell and squamous cell cancers) and melanoma. 

There are three main types of skin cancer found in the outermost layer of skin, the epidermis:

• Basal cell carcinoma (least serious and most common)
• Squamous cell carcinoma (more serious than basal cell carcinoma, but less common)
• Melanoma (most serious and least common)

The difference among the three is the type of cells that the cancer affects. In the case of non-melanoma skin cancers (i.e., basal cell carcinoma and squamous cell carcinoma), the cell affected is the keratinocyte. In human skin, this cell starts out at the basal layer (the lowest layer of the epidermis) and then moves up to the squamous (or middle ) layer of our skin. The non-melanoma cancers derive their names from where in the epidermis the affected keratinocyte is located.

Keratinocytes are the most common cell in the epidermis, the outermost layer of skin. These cells produce keratin, a tough, highly fibrous protein that acts as a barrier in our skin to provide waterproofing and prevent injury and invasion from microbes. This protein is also found in our hair, nails and tooth enamel.

You are more likely to develop a non-melanoma cancer if you have a family history of skin cancer, have already had skin cancer, or have fair or freckled skin, blue eyes and light-coloured or reddish hair. However, anyone who has had excessive sun exposure, severe and frequent sunburns during childhood, or lives in a sunny or high-altitude climate is at increased risk of developing skin cancer. Those who use immunosuppression drugs following an organ transplant, and other patients with suppressed or weakened immune systems are also at higher risk of non-melanoma cancer.

Although you can’t change some of these risk factors, some ways to reduce your risk include decreasing sun exposure, using sunscreen or long-sleeved clothing, avoiding sunburns, having regular skin check-ups, and avoiding tanning lamps and beds.

Looking Deeper
One of the primary causes of the DNA damage that leads to skin cancer is exposure to ultraviolet (UV) radiation from the sun and tanning lamps. However, genetic predisposition also plays a part. In fact, researchers have identified several genes that are linked to skin cancer. The "patched" (PTCH) gene often changes in basal cell carcinomas, while the p53 gene sometimes mutates in squamous cell cancers. While likely not the only genes associated with these carcinomas, they do give researchers some new clues in understanding these diseases.

Causes

Basal cell carcinoma: Most basal cell carcinomas are caused by exposing unprotected skin to the ultraviolet (UV) radiation in sunlight. The UV radiation damages genes that regulate cell growth and division. One gene commonly found to mutate (change) in basal cell cancers is the “patched” (PTCH) gene. Changes in this tumour-suppressor gene, which normally helps keep cell growth in check, can allow cells to grow uncontrollably. PTCH is unlikely to be the only gene that plays a role in the development of this skin cancer. Researchers are still working to fully understand the cause.

Nevoid basal cell carcinoma syndrome: This rare genetic condition is also known as Gorlin syndrome, or basal cell nevus syndrome. It is characterized by numerous basal cell carcinomas of the skin as well as jaw cysts seen on xray, palmar and plantar pits, calcified folds of the brain seen by radiography, hamartomas, various noncancerous growths, and skeletal anomalies affecting the ribs, hands and face.  Annual magnetic resonance imaging (MRI) for infants and children with the syndrome for medulloblastoma screening should be performed until the age of eight years. 

Squamous cell carcinomas: Most squamous cell carcinoma is caused by exposure of unprotected skin to ultraviolet (UV) radiation. Repeated, unprotected exposure to UV light, especially in the few years previous to diagnosis, increases the risk of developing squamous cell carcinoma. The UV radiation damages genes that regulate cell growth and division. People with weak immune systems are also at greater risk of developing squamous cell cancers. The gene commonly found to mutate in squamous cell cancers is called p53. Changes in this gene, which normally causes cells to die, may cause abnormal cells to live longer and perhaps become cancerous. Gene p53 is unlikely to be the only factor in the development of skin cancer. Researchers are still working to fully understand the cause.

Actinic keratosis (AK): This condition consists of one or more pre-cancerous skin lesions (pre-malignant). Thought not a cancer, some researchers believe it is an early form of squamous cell carcinoma. Only a small percentage of actinic keratoses go on to become squamous cell carcinoma.  The lesions are strongly associated with UV exposure and sun damage. (The words literally mean “sun-induced rough spots.”) Risk factors include being over the age of 40, exposure to high levels of UV radiation, and a weak immune system.

 Melanoma   Basal Cell Carcinoma  Squamous Cell Carcinoma Melanoma

 Fast Facts

• Non-melanoma cancer statistics are not well documented since many cases are successfully treated in a doctor’s office and are not reported. In fact, most provincial cancer registries do not require doctors to count non-melanoma cancers.
• When reported together, basal cell and squamous carcinoma are classified as “non-melanoma cancers.”
• Basal cell carcinoma comprises 80 per cent of non-melanoma cancers.
• Basal cell carcinoma can recur in the same or other places on the skin. Within 5 years of diagnosis, 35-50 per cent of patients develop a new skin cancer.
• Squamous cell carcinoma comprises 20 per cent of non-melanoma cancers.
• Actinic keratosis is one of the most commonly treated conditions by dermatologists.
• Only a small percentage of cases of Actinic Keratoses can become skin cancer.  Some cases go away on their own.
• In Canada, 74,100 new cases of non-melanoma cancers are estimated for this year; of these, 264 will likely be fatal.
• In the United States, approximately 1 million cases of non-melanoma cancer are diagnosed each year; of these, about 2000 result in death.

The most common sign of skin cancer is a local change in the skin’s colour or a sore that does not heal. However, skin cancer symptoms vary widely according to type, so it’s wise to check your skin regularly to catch any potentially cancerous marks early.

Basal Cell Carcinoma

This type of cancer begins in the lowest layer of the epidermis (the basal cell layer), usually on sun-exposed areas, such as the head, neck, and upper shoulders. However, 20% of people with basal cell carcinoma develop it in areas not exposed to the sun. This type of cancer grows slowly and rarely spreads to other parts of the body, but if left untreated, it will continue to grow and may ultimately invade the bone or other tissues beneath the skin. Basal cell carcinoma is usually treated successfully as an out-patient procedure. Symptoms include:

• A small, dome-shaped bump, frequently covered by small, superficial blood vessels
• A bump that is pearlescent, shiny or translucent
• May become scaly or crusty patches or open sores with a pearlescent or milky appearance and raised edges
• Bleeding after minor injury
• Growths enlarge may very slowly so subtle changes may not be noticed

Nevoid basal cell carcinoma syndrome

Skin growths are similar to basal cell carcinomas. In addition, the person may also have:

• Hamartomas (e.g. retinal) - overgrowth of normal cells
• Medulloblastomas  -  a low grade tumor of the brain
• Meningiomas -  localized benign growth of the cells lining the brain
• Calcified ovarian fibromas  - benign ovarian fibrous growth
• Cardiac fibroma -  non cancerous fibrous growth of the heart

Squamous Cell Carcinoma

This carcinoma begins in the upper layer of the epidermis (squamous cell layer), usually on sun-exposed areas, such as the head, neck and back of the hands. However, it may appear on skin elsewhere on the body (such as the lips, tongue or the lining of the mouth) and on skin that has been burned or exposed to chemicals or radiation therapy. Of these tumours, 95 per cent can be cured if found and treated early, particularly if they arise in areas of sun-damaged skin. Rarely, squamous cell carcinomas can grow and spread to lymph nodes. Symptoms include:

• Firm, red bump
• Scaly, bleeding or crusty growth or patch of skin
• Sore that does not heal
• As it grows, it may become raised and firm
• Eventually, it may appear like  an open sore (not always) and grows into the underlying tissue

Bowen’s disease isatype of squamous cell carcinoma limited to the epidermis. The affected area is red-brown and scaly or crusted and flat. It may resemble a patch of dermatitis, psoriasis, a fungal infection or a type of basal cell carcinoma.

Actinic Keratosis

These spots can look like regular skin, but may feel like sandpaper. Symptoms and signs include:

• Barely visible spots or localized red areas of skin
• May become thick, scaly and sometimes crusty patches of skin
• May change to a yellow-brown colour
• Visible spots may range between a few millimetres up to 2 cm or more in diameter.
• Skin discoloration, which may include dark or light pink, red skin 

To diagnose non-melanoma carcinomas, a doctor will take your medical history and perform a physical exam. If cancer is suspected, your doctor may take a skin biopsy, which will be used to confirm the diagnosis. A biopsy can be taken in one of four ways:

• The entire growth is removed.
• A sample of the area of concern is removed because the tumour goes into deeper layers of the skin. This technique is called “Shave and Punch”
• A “shave and punch” biopsy takes a sample through multiple skin layers.

A biopsy can be done in the doctor’s office or in a hospital’s outpatient department. It requires a local anesthetic and sometimes stitches, depending on how much skin is removed. The tissue sample will then be checked with a microscope to determine the diagnosis. .

Generally, the earlier non-melanoma skin cancers are caught, the more successfully they can be treated. Visit your doctor if you develop a new skin lesion that does not heal, notice a change in a pre-existing skin lesion (such as a mole), or have any of the symptoms or signs of non-melanoma carcinoma.

Treatment

Basal cell carcinoma treatments include the following:

• Surgery is often the primary treatment for basal cell carcinoma, and there are several different methods that can be used. An excision removes the tumour and surrounding skin. Curettage and electrodessication involves scraping the tumour from the skin and using an electric current to destroy any remaining tumour cells. Mohs surgery is a specialized technique that removes the visible tumour as well as an additional layer of tissue around the tumour.  This layer of tissue is examined with a microscope to identify any remaining cancer cells.  If this layer of tissue contains cancer cells the process is repeated until no tumour cells remain.  Lymph node removal is not usually required for basal cell carcinoma.
• Radiation therapy uses high energy rays or particles to kill cancer cells. It is primarily used for older people who cannot tolerate surgery. It is not the preferred treatment for younger patients because radiation may cause long-term damage. In external beam radiation therapy, a machine directs radiation to the tumour and surrounding area. Radiation therapy is often used for tumours on the ear, eyelid, lip and nose because it doesn’t remove normal tissue like surgery does. Topical drugs are most commonly used in chemotherapy for basal cell carcinoma. Topical 5-fluorouracil (5-FU) cream is applied directly to the tumour for several weeks or injected directly into the tumour. Only superficial tumours are treated this way as treatment does not reach tumours in the deeper layers of skin.
• Systemic drug treatments are rarely used for basal cell carcinoma. When they are used, the most common systemic agent injected intravenously is cisplatin.
• Biological therapy (immunotherapy) uses natural or manufactured agents to strengthen the immune system. Biological therapy is used only on low-risk, superficial basal cell carcinoma. Imiquimod is the most common biological drug used to treat basal cell carcinoma.

Nevoid basal cell carcinoma syndrome can be treated through:

• Surgery
• Photodynamic therapy has been used in some cases

Squamous cell carcinoma treatments include:

• Surgery
• Radiation therapy
• Chemotherapy
• Systemic drug treatments for squamous cell carcinoma are injected intravenously and include cisplatin, 5-FU, doxorubicin and mitomycin.

Actinic keratosis treatments involve:

• Lesion-directed: removal of a single or multiple skin lesions using procedures such as cryotherapy (freezing)
• Field-directed: treatment of an area of skin affected by AK through the application of topical creams or gels, or using photodynamic therapy

In addition to the treatments above, Canadian researchers are continually exploring new ways to treat non-melanoma skin cancers. Some may be conducting research studies known as clinical trials, which test new medications and treatments that are being developed. To learn about new research on all types of non-melanoma cancers happening in Canada, visit the clinical trials section [link to clinical trials section].

Footnote

*All information on medical treatments on this site is provided as an overview only. For a complete and up-to-date list of side effects, warnings and precautions, read the product’s package insert and consult your doctor or a pharmacist.

Although a cancer diagnosis is never welcome news, basal cell carcinomas are usually easily curable. With such high success rates, they usually do not negatively impact a person’s everyday life. However, patients may feel anxious knowing that their cancer may return, or may feel depressed if surgical removal of larger tumours leaves a scar or causes extensive damage to underlying tissues or bone.

Most squamous cell carcinomas are also easily treated and generally do not affect a person’s quality of life. In rare instances, people with this disease may suffer emotional trauma if their cancer progresses and requires long-term treatment or becomes life-threatening.

Non-melanoma skin cancers are curable most of the time, especially if caught early. With this, gentle reassurance alone is often sufficient to help someone successfully manage their fears. However, people with skin cancer who experience anxiety, depression or stress may seek professional counselling to manage their feelings or seek support from others who understand their situation.