Types of Skin Cancer in Singapore

Basal cell carcinoma arises from the basal cells in the deepest layer of the epidermis, the outer layer of the skin. It is the most common skin cancer in Singapore, accounting for 65.9% of the 12,692 skin cancers recorded between 1968 and 2016, and its incidence among Chinese Singaporeans rose 2.5-fold over that period (Oh 2021).

It typically presents as a shiny or pearly bump crossed by fine visible blood vessels, or as a small sore that bleeds, crusts and fails to heal. In Asian skin, basal cell carcinoma is often pigmented brown or black and is easily mistaken for a mole. It favours sun-exposed skin, with 81.3% of cases in Singapore arising on sun-exposed sites, most often the face and nose. The average age at diagnosis is 67 (Oh 2021).

Basal cell carcinoma very rarely spreads to distant organs. Untreated, however, it continues to invade the surrounding tissue, and this local destruction is most damaging around the nose, eyes and ears. Surgical excision with a clear margin is curative in most cases (Kim 2018).

Malignant melanoma arises from the melanocytes, the cells that produce skin pigment. It is the least common of the three, accounting for 5.8% of skin cancers in Singapore between 1968 and 2016, yet it is the type most likely to spread to the lymph nodes and other organs (Oh 2021).

It usually presents as a new dark spot or as an existing mole that changes. Its features are summarised by the ABCDE signs, an Asymmetric shape, an irregular Border, uneven Colour, a Diameter above 6 mm and Evolution over time (Abbasi 2004). A mole that looks different from all of a person’s other moles, known as the ugly duckling sign, is one of the strongest single indicators of melanoma (Gaudy-Marqueste 2017).

Melanoma follows a different pattern in Asian skin. About half of melanomas in Asian patients are acral lentiginous melanoma, which arises on the palms, soles and nail beds, compared with 2 to 3% in Caucasian patients. In a Singapore series, acral melanomas were diagnosed after a delay of 27 months, versus 12 months for other melanomas, and only 25% were detected at stage 1, versus 48% (Lee 2012). Only 26.7% of melanomas in Singapore occur on sun-exposed skin (Oh 2021). A dark streak in a nail or a dark patch on the sole therefore warrants examination. Atypical moles, which can resemble early melanoma, are discussed in atypical moles vs melanoma.

• A new spot that looks different from the surrounding moles.
• A mole that changes in size, shape or colour.
• A sore that bleeds, crusts and has not healed within four weeks.
• A scaly or rough patch that persists or recurs.
• A pearly or shiny bump, especially on the face.
• A dark streak along a nail, or a dark patch on the palm or sole.

Most skin cancers are painless in their early stages, so the absence of pain does not exclude cancer. A monthly self-examination in good light, including the scalp, palms, soles and nails, with photographs of any spot under observation, allows a change to be detected early.

Dermoscopy identifies which lesions require removal. A suspicious lesion is removed whole with a small margin, known as an excision biopsy, or sampled first when it is large. Histology at Singapore General Hospital confirms the type of cancer, its depth and whether the margins are clear, with results available in two to three weeks.

Surgical excision is the first treatment for all three types. I perform the surgery as a day surgery case in an MOH approved ambulatory surgery centre, so it is claimable under day surgery insurance, subject to your policy. Where histology shows that a wide local excision is needed, I refer the patient to our in-house plastic surgeon, and the operation is performed as a day surgery case. The treatment options are set out on the skin cancer treatment page, and the full pathway from screening to follow-up is described in the skin cancer guide.