Skin Cancer

Skin cancer is a common cancer.  The incidence rate of skin cancer worldwide has been rising rapidly.  Though the rate in Hong Kong is much lower than that in the West, the number of new cases continues to rise each year.  This is probably due to the increased participation in outdoor activities and aging population.  According to the Hong Kong Cancer Registry of Hospital Authority, there were 257 new cases of skin cancer in 2003 and 558 new cases in 2013. Non-melanoma skin cancer, the most common type of skin cancer, has been one of the top 10 cancers in Hong Kong. It rose from the 11th place in 2003 to the 7th in 2013.

While the incidence of skin cancer is high, its mortality rate is not that high.  Since skin is the most visible organ, it is easy for us to detect any abnormalities on the skin.  Hence, skin cancer can be treated early. If you notice any unusual changes in your skin, you should visit your doctor as soon as possible. Early detection increases the chance of successful treatment. 

(Special thanks to Dr. C. C. TONG, Associate Consultant, Clinical Oncology Department, Queen Mary Hospital for reviewing the information of this page)


Skin is the body's largest organ. Its major functions include protecting the body against injury, regulating body temperature through sweating, and preventing the body from becoming dehydrated.  The skin has three layers: epidermis (the top layer), dermis (the middle layer) and subcutis (the deepest layer).  The epidermis contains three main types of cells, including basal cells, squamous cells and melanocytes.

In general, healthy new skin cells push older cells toward the skin's surface, where older cells die and are sloughed off.  This process is controlled by DNA.  However, when DNA is damaged, malfunction will occur during the process, which may cause new cells to grow out of control and form cancer. Skin cancer usually develops on parts of the body that are often exposed to the sun, such as face, lips and neck. But it can also form on areas not ordinarily exposed to sunlight, such as palms, soles or the spaces between toes.



Skin cancers are named after the type of cell they develop from.  There are three major types of skin cancer: basal cell carcinoma, squamous cell carcinoma (non-melanoma skin cancers) and melanoma.  Other types of skin cancer, such as malignant skin tumors which arise from the sweat glands and hair follicles, are less common.

Basal cell carcinoma (BCC)
Basal cell carcinoma is the most common and most easily treated skin cancer.  It accounts for around 60% of all skin cancers.  It generally occurs in people over age 40.  Most BCCs appear on the head, nose, neck, and upper trunk.  Basal cell carcinoma usually begins as a pearly bump on the face, ears or neck.  When it develops on the chest or back, it appears as a scaly area or a patch of dry skin.  It may bleed or become ulcerated, and then heal and break down again.  It can recur in the same place on the skin.

Basal cell carcinoma usually grows slowly and almost never spread.  However, if left untreated, it will grow deeper into the skin and damage nearby structures.  This may make treatment becomes more difficult.

Squamous cell carcinoma (SCC)
About 30% of skin cancers are squamous cell carcinomas and most of them occur after age 50.  They usually begin as red nodules or ulcers and commonly appear on sun-exposed areas of the body such as the head, neck, hands and forearms.  They can also develop on the upper trunk and legs.  SCCs on lips or ears are more aggressive and are more likely to spread.

Although melanoma accounts for only 10% of all skin cancers, it is the most serious form and the one responsible for most skin cancer deaths.  Melanoma cells can grow fast and spread quickly to other body parts such as lungs, liver or brain even at early stages.

When melanoma occurs in Asian people, it usually develops on areas not normally considered to be sun-exposed, such as the soles, palms, fingernail beds or mucous membranes, etc.  Melanoma can start as a new pigmented spot on the skin.  It can also begin as a change in the size, shape or color of an existing mole or speckle.  The process may take several weeks to several months.  A melanoma usually has an irregular shape, a ragged border and uneven color. It raises above the surface of the skin and looks like a dirt. It can grow fast and have satellite lesions. You should see your doctor right away if you notice any of these characteristics. 


Research shows that 80% of skin cancers are preventable. The best way to prevent skin cancer is to protect your skin from the sun.  Here are some tips:

* Try to avoid the sun:
  - when the UV Index is 3 or above
  - between 11 a.m. and 3 p.m. when the sun rays are strongest

* Use sunscreen with sun protection factor SPF15+ and PA++ on all exposed skin, including the lips. Apply sunscreen 30 minutes before going out into the sun and reapply every 2 to 3 hours. SPF15 absorbs 93 % of UV radiation whereas SPF30 absorbs 97%. 

* Seek shade from trees, umbrellas, or any type of canopy.

* Wear a broad-brimmed hat, sunglasses, and dark, tightly woven clothing that covers your arms and legs.

* Avoid tanning beds and sunlamps.

* Be aware of sun-sensitizing medications. Some prescription and over-the-counter drugs can make your skin more sensitive to sunlight. These include certain high blood pressure, diabetes medications and acne medicines. Ask your doctor about the side effects of any medications you take. Take extra precautions if they increase your sensitivity to sunlight.

* Check your skin regularly. Examine your skin for changes in existing moles.  Check if they have changed in size, shape or color. With the help of mirrors, check your face, neck, scalp, back, hands, forearms, legs, feet, soles, and between your buttocks.


Skin cancers are mainly caused by exposure to ultraviolet (UV) radiation from the sun or other sources such as tanning machines in solariums. UV light is divided into three wavelength bands: UVA, UVB and UVC. UVB rays are responsible for many basal cell and squamous cell cancers. UVA also contributes to skin cancer, especially melanoma. Tanning beds deliver high doses of UVA and thus increase the risk of melanoma.

The damage caused by UV rays builds up over time. Even without causing sunburn, prolonged sun exposure over the years will cause damage to the skin tissue. Research shows that sun damage to skin cells can begin in childhood. Individuals who continue to receive excessive sun exposure without apt protection in adulthood can cause the already damaged skin cells to develop cancer.

Skin cancer can also occur on areas of the skin not ordinarily exposed to sunlight.  Heredity may play a role.

Anyone can get skin cancer, regardless of their skin color. You need to be especially careful if you:

 - have numerous moles
 - have pigmented spots (solar keratosis)
 - have a family history of melanoma
 - work outdoors under sunlight for a long period of time
 - have a history of sunburns, especially having skin peeling after severe sunburns
 - have fair skin that burns easily and doesn’t tan
 - have red or blond hair and light-colored eyes
 - have a weakened immune system due to HIV/AIDS or after an organ transplant
 - have fragile skin, such as skin that has been burned, injured or weakened by treatments for other skin      conditions, e.g. certain psoriasis treatments and eczema creams
 - have constant exposure to toxic chemicals


相片 Different types of skin cancer can look different. The most common symptoms are:

 - A new spot that is different from other spots on the skin around it.
 - A lesion that is itchy, painful or becomes inflamed.
 - A sore that does not heal.
 - A mole or spot that gets bigger, changes shape or color.
 - Be on the lookout for moles that:
           - have one half unlike the other half
           - have irregular or indistinct border
           - have many colors or an uneven distribution of color
           - are over 6 mm in diameter or get bigger
           - are raised from the skin with irregular shape


相片 If you notice any suspicious spots or moles, consult your doctor immediately. If your doctor suspects that you might have skin cancer, he or she will suggest that you have a biopsy. The procedure is quick and simple. You will have a local anesthetic; the doctor will remove a small sample of your skin from the suspicious area. You will then have a stitch or stitches to help the wound to heal. The sample will be sent to a laboratory where a pathologist will examine it under a microscope. It will take around a week to get the test results.


相片 Treatment for skin cancer varies, depending on the size, type, location and stage of the cancer. Doctors will adopt appropriate treatment according to the conditions of the disease.

Sometimes all of the skin cancer is removed during biopsy and no further treatment is needed.  If the cancer is large or has spread beyond the skin surface, more tissue will need to be removed.

Mohs surgery
This is microscopically controlled surgery that allows the cancer cells to be removed without taking an excessive amount of healthy tissue. The skin growth is removed layer by layer and examined under the microscope immediately. The removal continues until no cancer cells remain. This procedure is used to treat large skin cancers that have penetrated into the skin or have recurred.  It is also used for skin cancers in areas that are difficult to treat, like near the eye.

Cryosurgery is often used for people who are not able to have other types of surgery.  It is a freezing technique. Liquid nitrogen is sprayed over the growth on the skin to freeze and kill the cancer. The wound will be sore and red for a few days and may develop a blister. The dead tissue will later fall off. Healing can take up to a few weeks.  The treatment may leave a white scar.  

Electrodessication and curettage
This is common in treating superficial basal cell cancers.  A local anesthetic is given around the lump or spot, and the cancer is scooped out with a curette.  Electric current is then applied to stop bleeding in the area and to destroy any remaining cancer cells.  The wound will heal within a few weeks, leaving a pale scar.

This treatment is often used when the skin cancer is too large for surgery.  In general, anticancer drugs such as Imiquimod or Fluorouracil (5-FU) are applied directly to the skin to destroy cancer cells by stimulating the body's immune system. Chemotherapy is usually applied one or two times a day for up to six weeks.  The treated skin may become red, itchy, sore, and may scab or flake.  However, these side effects improve over time and it generally does not leave any scar.  

Photodynamic therapy (PDT)
PDT uses a light source and a special cream applied to the skin cancer to kill cancer cells.  It is mainly used to treat cancer on or near the surface of the skin.

First a light sensitive cream is applied to the skin and after a few hours a light is shone on the area.  The treated area will be covered with bandage to protect it from light afterwards.  Sometimes PDT needs to be repeated in 2-4 weeks.  People who have PDT need to avoid direct sunlight for at least six weeks after treatment.  After PDT, the skin normally heals quickly and without leaving a scar.

Some people may experience pain during PDT, particularly if having treatment on the face.  They can have a local anesthetic before the PDT to help ease the pain.

Radiotherapy uses one dose or many doses of high-energy rays to kill cancer cells.  It is generally used for older people or when surgery is not possible.  It is also commonly used in areas where surgery could be difficult, such as the eyelid, nose, forehead, ears, or for cancers that have grown too deep into the skin.  It may also be used for recurring cancers.

Side effects may occur during treatment period, such as the treated area may become red, swollen and painful.  However, these side effects will improve over time.  If a large area of skin has to be removed and the wound cannot be stitched, a skin graft or a reconstructive surgery is needed to repair the area.

In general, basal cell carcinoma and squamous cell carcinoma have a better prognosis. Melanomas have a higher risk of recurrence. Skin cancer patients should keep all follow-up appointments.  To prevent recurrence of the disease, they should also examine the skin regularly for any unusual moles, spots or sores that do not heal.

After surgery or treatment, it is important to follow the doctor's advice on bathing, exercise or other activities.  Skin cancer patients can participate in outdoor activities; just be sure to take sun exposure precautions.  Surgery nearly always leaves some type of scar.  You don't have to worry about what others will think of the scar. Participating in social activities as usual and this can help to relieve emotional distress. 

Research shows that antioxidants in food such as beta-carotene and Vitamin E help protect against UV skin damage and prevent skin cancer.  Foods that are rich in beta carotene include carrots, sweet potatoes, papaya and apricot, etc.  Besides, foods with rich Vitamin E include olive oil, leafy green vegetables, wheat germ, beans, berries and nuts.

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  • Regeneration Society Ltd
  • Hong Kong Cancer Fund
  • NHS, UK
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