The skin is the largest human organ. It serves as the interphase protecting the individual from the environment. One of the biggest insult to the skin is ultraviolet (UV) radiation from the sun. UV radiation is a trigger for many skin tumours/growths. Some of these growths are benign and can be left alone. Some however are cancerous and must be removed early. These lesions are called malignant tumours.
Some common malignant skin tumours are:
1. Basal Cell Carcinoma (BCC)
This is the most common malignant skin tumour worldwide. It is a slow growing skin cancer and up to 80% of all BCCs occur on the head and neck especially on the nose. The cancer often presents as a longstanding ulcer with a shiny or pearly raised margin. It is often painless. Chronic sun exposure is a factor in the development of basal cell carcinomas.
Fig 1: BCC over the right cheek
2. Squamous Cell Carcinoma (SCC)
This is 2nd most common form of skin cancer. It commonly presents as a firm irregular fleshy growth usually on sun exposed skin (Fig 2). The tumour can grow quickly and has the potential to spread beyond the skin. Chronic sun exposure is an important contributing factor in the development of this type of skin cancer. Tobacco products are a significant risk factor for lip and oral SCC.
Fig 2: SCC arising on the forearm of an elderly gentleman.
3. Malignant Melanoma
This is a serious form of skin cancer arising from the pigment cells (melanocytes) of the skin.It can occur on any site, including the palms and soles, and it has a tendency to spread to surrounding lymph nodes or other parts of the body. It often presents as a dark brown or black skin growth or ulcer. It may look like ordinary moles but some red flags include:
Asymmetry in the shape
Evolving (change in shape/ colour/ size)
Those with a family history of melanoma, or have a history of excessive sun exposure or sunburns are at increased risk of developing melanomas.
Fig 3: An evolving “mole” which when viewed with a dermatoscope revealed irregular dots and globules that prompted an excision biopsy. The histology was consistent with a malignant melanoma.
Diagnosis of skin cancers
Any skin lesion that is progressively enlarging should be assessed and examined by a trained doctor. Contrary to popular belief, malignant skin tumours do not always cause pain, so this symptom is not reliable. If a skin cancer is suspected, your doctor may advise and order a biopsy under local anaesthetic for microscopic examination. Upon confirmation of a malignant skin tumour, the doctor can assess and advise the best option for treatment.
The most common form of treatment of a malignant skin tumour is surgery. There are 2 surgical options: standard wide excision and Mohs micrographic surgery (MMS). MMS involves surgically removing skin cancer layer by layer like peeling an onion, mapping the excised specimen and examining the entire margins of each layer under the microscope. This facilitates the complete tracing of the tumour roots until healthy, tumour-free tissue is reached (Fig 4).
MMS thus ensures the highest possible success rate. In fact, reported 5 year cure rates for primary skin tumours treated by MMS is 99% versus 93% for standard excision. Standard surgical excisions involve excising the tumours with a predetermined margin and assessing the excised specimens in the pathology laboratory either with a “breadloaf” or “quandrant” method. These methods leave marginal areas between the sections not microscopically visualised. In fact, it has been shown the above techniques only evaluate about 1% of total margins. The failure to detect subclinical microscopic tumour foci may result in tumour recurrence in spite of “clear” margins on histology report.
Furthermore, as the tumour roots are being traced and only tumour involved tissues are removed, the technique is also considered to be tissue sparing and is of great value in the excision of tumours occurring in cosmetic sensitive areas like the “H-zone” of the face (around the eyes, mouth and, nose) and the ear, to maximize cosmetic and functional outcome post surgery.
In addition, as there is greater confidence of clearance of the tumour, the resultant defect can be better managed. Surrounding skin can be mobilized to facilitate closure and hiding the scars at cosmetic subunits junctions, thus achieving better cosmetic outcome.
Fig 4: BCC to the right the nose. The tumour was debulked and a layer was harvested, mapped, and prepared for microscopic examination of the entire margins
In certain situations whereby complete excision may not be feasible, other forms of therapy such as radiotherapy, photodynamic therapy or topical therapy may be used.
Skin cancer is not uncommon. It ranks among the top 10 cancers among the males and females in Singapore. There is a rising incidence of skin cancer and this can be attributed to the change in lifestyle and behaviour. Early detection and treatment gives the best possible outcome.