What causes skin cancer?
Cumulative sun exposure is the most common cause of skin cancer. Ultraviolet radiation (UV) from the sun causes damage to the DNA in the skin which results in pre-cancerous and cancerous lesions. Researchers believe that long-term cumulative sun exposure predisposes one to non-melanoma skin cancer such as basal cell carcinoma and squamous cell carcinoma. Whereas episodic severe sunburns, especially in young age, are more likely to cause melanoma. UV from tanning beds is just as harmful as those from the sun and should be avoided.
Less common causes of skin cancer include repeated radiation exposure (e.g. from x-rays or CT scans), unstable burn scars or chronic wounds (Marjolin’s ulcers). Certain chemicals, and some rare genetic disorder (e.g. xeroderma pigmentosum).
What are the different types of skin cancer?
There are three major types of skin cancers: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. There are other types of skin cancers (e.g. Merkel cell cancer) but they are relatively rare.
BCC is the commonest, and fortunately least aggressive, skin cancer. It is mostly found in the sun-exposed areas, frequently on the face but also seen on the limbs and upper chest. BCC rarely spreads to the lymph nodes or other parts of the body. The chance of cure is high as long as the lesions are excised (surgically removed) promptly.
SCC is also common in sun-exposed areas of the body. These lesions tend to be more scaly in appearance and have a higher tendency to spread to lymph nodes. Proper assessment of the lymph nodes that drain the skin cancer sites (e.g. neck, axilla) is important while planning for the removal of SCC.
Melanoma is the most aggressive of the three types of skin cancer. They can appear in nearly any part of the body, sun-exposed or not. If not diagnosed and treated promptly, melanoma can spread to lymph nodes and distant organs, potentially rendering it incurable.
How frequently should we check our own skin and how often should we visit a professional to check our skin?
There is no official guideline on frequency of skin checking. However, periodic assessments facilitate early diagnosis of skin cancer when treatment is easiest and most effective. This is especially important for those with risk factors, e.g. family history, individuals with atypical moles (e.g. dysplastic naevus) or many common moles, and individuals with pre-cancerous lesions (e.g. actinic keratoses).
Initial presentations of most skin cancers are skin changes which are fairly noticeable for those who are conscious about skin cancers. When the doctor deems a lesion clinically suspicious, a biopsy will usually be performed. Proper investigation and treatment will be performed once the histology and staging of the skin cancers are confirmed.
It is also very important to follow up after cancer treatment. Not only will the doctors monitor for local and systemic recurrences, but it is also important to screen for any second primary (metachronous) cancers.
Who is most at risk of getting skin cancer?
Those who have heavy UV exposure are at risk of getting skin cancer, be it from the sun, tanning beds, or other sources. Other risk factors include repeated radiation exposure (e.g. from x-rays or CT scans), unstable burn scars or chronic wounds (Marjolin’s ulcers), certain chemicals, and some rare genetic disorder (e.g. xeroderma pigmentosum).
Family history is a risk factor for melanoma. The risk of melanoma also increases in those who have atypical moles (dysplastic naevi) or many common moles.
What are the signs and symptoms of skin cancer?
- Skin cancer typically develops in sun-exposed skin, such as the face, ears, scalp, neck, upper chest, and upper limbs, although sometimes they can develop in other areas as well. Different types of skin cancers have different appearances.
- Basal cell carcinoma tends to appear as a pearly or waxy lump which is sometimes ulcerated. They tend to be pigmented in Asians.
- Squamous cell carcinoma on the other hand tend to present as a scaly, crusted lesion. They may present as a cutaneous horn sometimes.
- Melanoma has a wide range of presentation. They can develop on any part of the body, even under the nails. Melanoma may present as a brownish spot that is heterogeneously pigmented (i.e. contain both darker and lighter speckles).
- In general, one should rule out skin malignancy in any ulcer that fails to heal in three weeks, any lesion that is gradually growing in size, and any mole that has been changing in size and appearance. It is safest to consult a dermatologist for a proper assessment, documentation, and biopsy if necessary.
What is the typical treatment?
For basal cell carcinoma, wide excision with adequate resection margins are usually adequate for cure. Lymph nodes and systemic workups are rarely necessary.
Squamous cell carinoma is more likely to have nodal spread and lymph node assessment is therefore advisable before surgery. If there is a confirmed lymph node involvement, lymph node dissection is needed in addition to wide excision of the tumour itself.
Melanoma also requires lymph node assessment, and sometimes even systemic workup (e.g. by PET-CT scans). Melanoma generally requires a wider resection margins than basal and squamous cell carcinoma. If there is a lymph node involvement, lymph node dissection will be performed in addition to wide excision of the tumour itself. However, even when there is no clinical evidence of lymph node involvement, sentinel lymph node biopsy may still be necessary for more advanced melanoma.
Need for additional treatment (e.g. radiotherapy) is usually unnecessary for basal cell carcinoma, but may be needed for some cases of squamous cell carcinoma and melanoma.
How common is skin cancer in Hong Kong?
According to the latest data (2017) from Hong Kong Cancer Statistics, non-melanoma skin cancer is the 7th most common skin cancer in Hong Kong (both genders combined). There were 1,190 new cases of skin cancer (melanoma and non-melanoma) in 2017. The overall incidence rate (per 100,000 persons) was 16.1 with the highest incidence of 61.4 in the 65+ age group.
What are the best ways to prevent skin cancer?
The best way to prevent skin cancer is sun (UV) protection and awareness. We should limit our sun exposure and avoid going under the sun unprotected. Both types of UV radiation, UVA and UVB, from the sun are carcinogenic so it is important to ensure both when looking for sun protection. When choosing sunblocks, note both SPF and PA values. SPF reflects UVB protection only, UVA protection is reflected by the PA value. Choose SPF 30 or above AND PA +++ or PA ++++. It is even better if it contains physical sunscreen, such as titanium dioxide or zinc oxide as they protect against both UVA and UVB, are photo-stable, and are less irritating to the skin. It should also be noted that most people under apply sunscreens. The proper amount of sunscreen should be 2mg/cm2 of skin, which translates to about 30g for full body coverage). Sunscreen should also be reapplied every 2 hours.
Be sure to seek prompt medical attention and consider biopsy when:
1. An skin lesion/ulcer takes more than 3 weeks to heal.
2. A skin lesion is resistant to treatment with a topical ointment or cryotherapy (freezing off).
3. A growing lesion or one which is changing appearance.
Hong Kong based mum of two, Adele Hughes shares her story after being diagnosed with Melanoma in 2019. Read her blog to learn about her journey.
This post was originally written in June 2020 and updated in Feb 2021.
Read More: Sun Safety Tips & Sunscreen Recommendations