Skin Cancer

Skin cancer is the abnormal growth of skin cells, usually caused by ultraviolet radiation exposure, leading to malignant tumours that can spread if untreated.

Skin cancer begins in the skin’s top or outermost layer – the epidermis. The epidermis is a thin layer that provides a protective cover for the body, keeps skin hydrated, produces new skin cells and contains melanin, which determines skin colour. There are three main types of cells in the epidermis:

• Squamous cells lie just below the outer surface and function as the skin’s inner lining 
• Basal cells sit beneath the squamous cells and produce new skin cells 
• Melanocytes are located in the lower part of the epidermis and produce melanin, the pigment that gives skin its normal colour 

What are the types of skin cancers?

Skin cancers are divided into melanoma (MSC) and non-melanoma skin cancer (NMSC).

• Melanoma
  Melanoma refers to the malignant tumour of the melanocytes which behave aggressively. It can develop anywhere on the body, in otherwise normal skin or in an existing mole that turns cancerous. In Asia, acral and mucosal melanomas are more common than cutaneous melanomas. Acral melanomas occur in palms, soles and nails while mucosal melanomas arise from internal tissues. In Singapore, the incidence of melanoma skin cancer is relatively low with 0.5 cases per 100,000 persons. 
  
  
• Non-melanoma skin cancer (NMSC)
  Non-melanoma skin cancer refers to all the types of skin cancer that are not melanoma, such as basal cell carcinoma and squamous cell carcinoma.
  
  Non-melanoma skin cancer slowly develops in the upper layers of the skin.
  
  In Singapore, non-melanoma skin cancer is much more common than melanoma skin cancer. Non-melanoma skin cancer is the 6th most common cancer in males in Singapore and the 7th most common cancer among females in Singapore. 

Rare skin cancers

• Merkel cell carcinoma – this is a rare and aggressive type of skin cancer which can affect older adults with lighter skin pigmentation. 
• Kaposi’s sarcoma can occur in different forms and it is often associated with immunosuppression. 
• Skin lymphomas – more information is available in the Lymphoma segment.

Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms and hands. However, it can also form on areas that are rarely exposed to the sun, such as beneath the palm, fingernails or toenails and the genital area.

Melanoma skin cancer

Lopes, J., Rodrigues, C. M. P., Gaspar, M. M., & Reis, C. P. (2022). Melanoma Management: From Epidemiology to Treatment and Latest Advances. Cancers, 14(19), 4652. https://doi.org/10.3390/cancers14194652

Symptoms of melanoma skin cancer may include:

• The appearance of a new mole or a change in an existing mole 
• A large brownish spot with darker speckles 
• A mole that changes in colour, size or texture 
• A bleeding mole 
• A small lesion with an irregular border and portions that appear red, pink, white, blue or blue-black 
• A painful lesion that itches or burns 
• Dark lesions on the palms, soles, fingertips or toes or on mucous membranes lining the mouth, nose, vagina or anus

Non-melanoma skin cancer (NMSC)

Symptoms of non-melanoma skin cancers may include:

• Basal cell carcinoma 
  • A pearly or waxy bump 
  • A flat, flesh-coloured or brown scar-like lesion 
  • A bleeding of scabbing sore that heals and returns 
• Squamous cell carcinoma 
  • A firm, red nodule 
  • A flat lesion with a scaly, crusted surface 

When should you see a doctor?

You should see a doctor if you notice any changes to your skin that concern you, particularly if a mole or spot changes in size, shape or colour; becomes itchy, painful or bleeds; develops an irregular border or uneven texture; or does not heal after several weeks.

Most skin cancers are preventable. There are several ways to lower the risk of skin cancer:

• Avoid sun exposure during the middle of the day (10am-4pm).
  • Excessive exposure to ultraviolet (UV) rays in sunlight increases the risk of developing skin cancer. Avoiding the sun at its strongest helps to avoid the sunburns and suntans that cause skin damage and increase the risk of developing skin cancer.
  • Sun exposure accumulated over time may also cause skin cancer.
• Apply sunscreen all year-round, including when indoors, on cloudy days or overseas in cold weather
  • Sunscreen should be used every day, and works best when it is applied 15 minutes before going outdoors. It should be reapplied every two hours or more frequently, especially when engaging in water sports or sweating a lot.
  • Use a broad spectrum sunscreen that protects against both UVA and UVB, the Sun Protection Factor (SPF) of the sunscreen should be at least SPF 30 or higher. While higher-number SPFs can block slightly more of the sun’s UV rays, it is important to note that higher-number SPFs do not give longer protection and must be re-applied as frequently as sunscreens with lower SPF.
  • Apply a generous amount of sunscreen on exposed skin, including the lips, the tips of your ears, and the backs of your hands and neck.
• Wear sun-protective clothing
  • As sunscreens do not provide complete protection from UV rays, it is important to cover your skin with dark, tightly woven clothing that covers your arms and legs, and a broad-brimmed hat, which provides more protection than a baseball cap or visor does.
  • Use sunglasses that block both types of UV radiation — UVA and UVB rays.
• Avoid tanning beds as the lights used in tanning beds emit UV rays that can increase the risk of skin cancer.
• Ask your doctor or pharmacist about the side effects of any medications you take. If they increase your sensitivity to sunlight, take extra precautions to stay out of the sun to protect your skin.
• Examine your skin often for new skin growths or changes in existing moles, freckles, bumps and birthmarks. Make an appointment with your doctor if you notice any changes that worry you.

What causes skin cancer?

Skin cancer develops when skin cells undergo genetic mutations, leading to abnormal and uncontrolled growth. The primary cause is ultraviolet (UV) radiation from the sun or artificial sources like tanning beds, which damages DNA in skin cells over time. This damage disrupts normal cell function, allowing mutated cells to multiply unchecked. In some cases, genetic factors or exposure to harmful substances can also contribute to these mutations, triggering cancerous changes.

What are the risk factors for skin cancer?

• Excessive sun exposure 
• Tanning, including exposure to tanning lamps and beds 
• Moles – having many moles or abnormal/atypical moles  
• Fair skin – having less pigment (melanin) in the skin provides less protection from UV rays and causes the skin to burn easily 
• Family or personal history of skin cancers 
• A weakened immune system (due to a medical condition or medicine that affects the immune system) 
• Sunny or high-altitude climates 
• Pre-cancerous skin lesions (actinic keratosis) 
• Exposure to radiation and substances such as arsenic

Tests and procedures used to diagnose skin cancer include:

• A physical examination using a dermatoscope to determine whether the skin changes are likely to be skin cancer.
• A skin biopsy is a minor procedure usually done under local anaesthetic (where you are conscious) where a tissue sample of the suspicious skin growth is taken and sent to the lab for testing and analysis.

In some cases, skin cancer can be diagnosed and treated at the same time. The tumour is removed and tested and you may not need further treatment if the cancer is unlikely to spread.

In other cases, once skin cancer is confirmed, further tests may be needed to determine the extent (stage) of the cancer and the most suitable treatment. The tests may include:

• Blood test
  Blood tests are done to determine baseline organ function.
• Imaging tests
  Imaging in the form of CT scan or PET CT scan are done to determine the extent of the disease and distant spread.
• Lymph node biopsy
  A lymph node biopsy involves the removal of a small amount of lymph node tissue for laboratory testing to check for signs of cancer.

There are a few effective treatment options for skin cancer. In general, treatment for skin cancer depends on the following factors:

• Size, type, depth and location of the lesion
• Stage of the disease when the cancer is found
• The patient’s general state of health

The main treatment for skin cancer is surgery. However, some patients may also require other treatments such as chemotherapy, radiotherapy, or cryotherapy.

An individual with cancer should be assessed by a specialist to determine which treatment is best suited for them.

Surgery

• Excisional surgery
  This procedure is appropriate for any type of skin cancer. The cancerous tissue and surrounding margin of healthy skin will be cut out (excised). A wide excision – removing extra normal skin around the tumour – may be recommended in some cases. Nearby lymph nodes may be removed and biopsied to stage or treat localised spread of the tumour.
• Mohs micrographic surgery
  This procedure is used to remove larger, recurring or difficult-to-treat skin cancers, which may include non-melanoma skin cancers such as basal and squamous cell carcinomas. It is often used in areas where it is necessary to conserve as much skin as possible, such as on the nose.
  
  During the surgical procedure, the skin growth is removed layer by layer, the doctor will examine each layer under the microscope and surgery continues until no abnormal cells remain. This procedure allows cancerous cells to be removed without taking an excessive amount of surrounding healthy tissue.

If the skin defect after surgery is large, our surgical oncologists will work with a plastic surgeon to provide reconstructive services to restore a natural appearance. The multidisciplinary team will ensure good oncology treatment and aesthetic reconstruction for best outcomes.

Freezing (cryotherapy)

Cryotherapy refers to the use of liquid nitrogen to freeze and destroy pre-cancerous skin lesions (actinic keratosis) and some small early skin cancers. Freezing causes the cancerous tissue to die and form a scab that will naturally fall off in time.

Curettage and electrodessication

This is a simple and quick procedure used to treat basal cell cancers or thin squamous cell cancers. After removing most of the skin growth, the doctor scrapes away layers of cancer cells using a device with a circular blade (curet). An electric needle is then used to destroy any remaining cancer cells.

When necessary, this procedure may be used in combination with cryotherapy (see above).

Radiotherapy/ Radiation therapy

Radiotherapy also known as radiation therapy uses powerful energy beams to kill cancer cells. It may be used when the cancer cannot be completely removed during surgery.

Systemic therapy

For skin cancers confined to the top layers of the skin, topical treatments such as creams or lotions containing anti-cancer agents may be applied directly to the affected area.

However, when the cancer is more advanced or has spread beyond the skin, systemic therapy may be needed. Systemic therapy refers to treatments that circulate throughout the body to target cancer cells wherever they may be. This includes:

• Chemotherapy: Chemotherapy involves the use of drugs that kill rapidly dividing cancer cells. It may be used in cases where the cancer has spread or is not amenable to surgery or radiation. 
• Immunotherapy: Immunotherapy works by stimulating the body’s immune system to recognise and attack cancer cells. It is increasingly used in advanced melanoma and certain non-melanoma skin cancers. 
• Targeted Therapy: Targeted therapies are drugs designed to attack specific genetic mutations or molecular markers present in cancer cells. These treatments are often more precise but they can only be considered if the specific genetic mutations are present. 

For the rest of the body, chemotherapy (injected into a vein or taken orally) can be used to treat skin cancers that have spread to other parts of the body.

In patients with advanced skin cancer, chemotherapy may be used alone or with surgery, immunotherapy and radiotherapy.

Photodynamic therapy

Photodynamic therapy destroys skin cancer cells with a combination of laser light and drugs that makes cancer cells sensitive to light.

How can you prepare for skin cancer surgery?

If surgery is required, your surgeon will perform comprehensive medical assessments including blood tests and scans, to see if you are suitable and advise on the risks involved. Your treatment recommendation is often based on consensus by a group of medical specialists' opinions (the tumour board), who come together to discuss the benefits and limitations of every treatment strategy.

The anaesthesia team will also assess your fitness for surgery and advise you on various aspects of general anaesthesia and pain control after surgery.

Specialist nurses will also provide pre-surgery counselling so that you know what to expect.

What can you expect after skin cancer surgery?

After surgery, you will be given regular outpatient appointments to see your team of doctors. During these appointments, you may have blood tests and scans to check if the cancer recurs.

It is important to follow your doctor's advice, keep to your clinic visits and do the recommended scans, so that timely treatment can be administered if the cancer or other problems occur.

• What does melanoma look like?
  Melanoma often appears as an irregular mole with uneven borders, multiple colours or rapid growth. The ABCDE rule helps identify it: Asymmetry, Border irregularity, Colour variation, Diameter over 6mm and Evolving changes. 
• Can skin cancer return after treatment?
  Yes, skin cancer can recur, especially if there is continued sun exposure. Regular skin checks and follow-ups with a doctor are important to detect any recurrence early. 
• Is sunscreen enough to prevent skin cancer?
  Sunscreen helps reduce the risk but should be used alongside other protective measures such as wearing hats, sunglasses and protective clothing and seeking shade during peak sun hours. 
• Can children get skin cancer?
  Yes, but it is rare. Excessive sun exposure during childhood increases the risk of developing skin cancer later in life. Sun protection from an early age is important. 
• How often should I check my skin for changes?
  It is recommended to check your skin once a month for any new or changing moles or lesions. A professional skin examination should be done annually, especially if you have risk factors.