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Skin Cancer

Skin Cancer - What it is

Our skin is made up of epidermis, dermis, subcutaneous tissue, and other adnexa within the layers. Epidermis is a kind of squamous epithelium. In the epidermis, the actively dividing basal cells mature to become keratinocyes. Subsequently, the keratinocyes die and become keratin. Interspersed between the basal cells are pigment-producing cells called melanocyes. Skin cancers are malignant tumours of the basal cells, keratinocyes and melanocytes.

How common is Skin Cancer?
Skin cancer is one of the top ten most frequent cancers in Singapore. There has been a general rising trend in the incidence of this cancer in both men and women over the last 40 years. According to the Trends in Cancer Incidence in Singapore 2014-2018 (Singapore Cancer Registry), there were 1,975 and 1,568 cases of skin cancer reported in Singapore men and women respectively. Skin cancer ranks 6th in male cancers and 7th in female cancers in Singapore.

Anecdotally there seems to be more young people (<65 years old) being diagnosed with skin cancer recently, however data from the cancer registry indicates that this condition is still most prevalent in the elderly. This apparent trend could be as a result of increased awareness regarding the disease and more health-seeking behavior among the younger population, as well as easy access to medical care for earlier diagnosis and/or treatment.

Types of Skin Cancer

Skin cancers are divided into melanoma and non-melanoma skin cancer (NMSC). In Singapore, NMSC are much more common than melanoma. Melanoma behaves much more aggressively than NMSC. Melanoma is the malignant tumour of the melanocytes. NMSC consists of squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). In normal population, BCC is more common than SCC. Solid organ transplant recipients have higher rate of skin cancer and SCC is the more common subtype.

Skin Cancer - Symptoms

Many patients first consult a doctor because of a lump or mass on the trunk, leg, or arm. The lump may or may not be painful.  Melanomas are usually self-detected. This means the patients or their close relatives usually notice a mole on their body which has appeared in the recent few weeks, or is irregular in shape and colour, increasing in size or bleeds easily. The acral type melanomas can appear as a black/brown spot under the nail or on the soles of the foot and palms of the hand. 
When advanced, skin cancer can involve the underlying deeper layers and result in destruction of surrounding issues. It can also spread to regional lymph nodes and distantly to involve other organs. At this stage, skin cancer cannot be cured by simply removing the affected mole, and may require more extensive surgery, or even additional treatment like chemotherapy, radiation and immunotherapy to achieve control.
The cancer is diagnosed when biopsy (removal of piece of tissue) of a lump on the arm, leg or trunk is examined under a microscope by the pathologist (doctor who specializes in examining tissues and cells). 

Skin Cancer - How to prevent?

Excessive exposure to the ultraviolet (UV) rays in sunlight is a risk factor that increases one’s risk of developing skin cancer, and we definitely still need sun protection even if we are not outdoors, or on cloudy days, or during travels in wintertime. Sun avoidance and the use of sun protection devices such as hats, umbrella, clothing and sunscreen should be started from young. Self-examination and awareness can help early detection of skin cancer.

Sunscreen should be used every day, and works best when it is applied 15 minutes before going outdoors, and should be reapplied approximately every two hours (or more frequently if you are engaged in water sports or sweating a lot). Use a broad spectrum sunscreen that protects against both UVA and UVB, with at least SPF 30 or higher, as higher-number SPFs can block slightly more of the sun’s UV rays, but it is important to remember that higher-number SPFs does not give you longer protection without frequent reapplication.  

Skin Cancer - Causes and Risk Factors

BCC is the most common type of skin cancer and is most common in the sun-exposed area. The most common complaint is bleeding or scabbing sore that heals and recurs. BCC is slow growing and may grow for many years before presentation to the doctor. There are several types of BCC. In Singapore, the pigmented BCC is relatively common and may be mistaken for a mole. Although BCC can be locally destructive, it rarely spreads (metastasizes).
SCC is the second most common skin cancer in Singapore. There are 3 types of presentation of SCC. SCC may arise from actinic keratoses that look like thick scaly patches stuck on the skin. These SCC are soft and freely movable and are located on the bald scalp, forehead, ears, and backs of the hands. The second type of SCC appears in sun-damaged skin. They are firm, movable, elevated lumps with sharply defined border and few scales on the surface. These SCC have minimal potential to metastasis but may be locally aggressive. The third type of SCC arises from normal skin or the lip. They are aggressive and metastasizes to regional lymph nodes.
Melanoma is the most dangerous skin cancer because of its tendency tometastasize early. There are several types of melanoma. The acral lentigenous melanoma is the most common type of melanoma in Singapore. They appear on the palms, soles or the under the nails of toes and fingers. The melanoma may arise from normal appearing skin or an existing pigmented growth. The ABCDE rule of melanoma stands for Asymmetry, Border, Colour (haphazard combination of many colours), Diameter over 6 mm and Evolving (enlarging) of a pigmented growth. Therefore, it is important to consult a doctor if there is any change of a growth on the skin.
Ultraviolet radiation from the sun is the most important risk factor of melanoma and NMSC. In addition to sun exposure, fair skin individuals (who also typically have lighter hair and eyes) are at higher risk of developing skin cancer as they have less melanin ( a pigment in the skin) to protect themselves from the UV rays. Risk factors for melanoma include sun exposure, family history or personal history of melanoma, history of atypical moles, and age. Individuals with a first-degree relative diagnosed with melanoma has a 50 percent greater chance of developing the disease than people who do not have a family history of the disease.   

Skin Cancer - Diagnosis

Skin biopsy is used to diagnose skin cancer. It is a simple procedure done under local anaesthesia. Either part of the suspected growth or the whole growth if it is small is removed and sent to the pathologist. The pathologist will examine the specimen under the microscope and confirm the diagnosis. The pathologist will also determine the histologic type (cell type of the cancer cells), the thickness of the cancer (depth of invasion) and other characteristics of the skin cancer.
Other tests such as lymph node biopsy, blood test and imaging may be required for staging, treatment and prognosis.

Skin Cancer - Treatments

The mainstay of treatment is surgical excision with adequately wide margins. There are guidelines to the excision margins of the various skin cancers. If the skin defect is large after excision, skin graft may be required to cover the wound. Moh’s microsurgery is a microscopically guided procedure to remove skin cancer. Other forms of treatment include cryotherapy (freezing with liquid nitrogen), curettage and electrosurgery, photodynamic therapy and radiation therapy. FDA has approved imiquimod cream to treat superficial BCC and SCC. Metastatic melanoma can be treated with interferon alpha-2b, interleukin 2 and chemotherapy.

Prognosis of Skin Cancer
Treatment and survival outcomes depend on the stage of the skin cancer when it is diagnosed. The prognosis depends on the histologic type of the malignant cell, tumour size, depth of the tumour, location of the tumour and the presence of metastases. Wide excision can potentially be curative for many early skin cancers. At an early stage, surgery is usually all that is needed for treatment. However, when the skin cancer is more advanced i.e. stage 3 or 4, then it is usually treated with a combination of surgery, chemotherapy, immunotherapy and radiotherapy. The early detection of skin cancer cannot be overemphasized. The only risk factor for skin cancer which can be avoided is sun exposure. In patients with a strong family history, or with multiple moles, regular examination by a skin doctor can help with early detection and treatment in the event of a skin cancer.. All patients should be followed up to detect local recurrence, metastases and additional skin cancers after treatment.

Skin Cancer - Preparing for surgery

Skin Cancer - Post-surgery care

Skin Cancer - Other Information

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