Did you know that skin cancers are the most common type of cancer in the world? Skin cancers are generally regarded as problems of light-skinned individuals. True, among the different skin phototypes, those that burn easily and do not tan well have higher risk for developing cutaneous malignancies. It cannot be overemphasized how the sun can damage the DNA in our skin cells, causing mutations and malignancies. Without the protective effect of melanin, those with fair skin stand to suffer more damage. However, brown or dark-skinned people should not be complacent. Skin cancers in this population are not uncommon! Melanin is not completely protective, and not all skin cancers are due to sun damage. In a comprehensive review of skin cancers among skin of color, it has been found that skin cancers in this population are often associated with greater morbidity and mortality![i] BCC, SCC and melanoma are the 3 most common types of skin cancer. Basal cell carcinomas (BCC) are considered indolent, slow growing and non-fatal, but they may cause significant disfigurement. Squamous cell carcinomas (SCC) are more aggressive, may metastasize, and can be fatal. The most aggressive form is melanoma, usually arising from or near a mole, and highly fatal if not detected early.
What are the risk factors?
Sun exposure and tanning beds
Ultraviolet radiation is a primary risk factor. The dose or intensity of exposure depends on the degree of skin pigmentation and the location of the person, with lower latitudes (nearer the equator) receiving more exposure to UV rays. Use of tanning beds also predisposes one to skin cancer, especially BCCs and SCCs. Brief, intermittent and repeated sun exposure (such as during summer vacations in the tropics) early in life is associated with the development of BCC.[ii] Studies on basal cell carcinomas among Filipinos show that the head and neck -specifically, the nose and lids- are common sites[iii]. Among Caucasians, SCCs are also often found in sun-exposed areas. Chronic, cumulative exposure is a key risk factor. These lesions often develop from actinic (solar) keratoses, a type of pre-malignant lesion that initially feels rough like a sandpaper, and eventually may appear as thick, scaly , crusty papules or plaques, and often found on the scalp, face, neck, forearms, and back of the hands.
Chronic scarring or irritation
On the other hand, among skin of color, SCCs are not commonly found in sun-exposed areas! They are more often found in sun-protected sites such as legs , feet, and anogenital area, although the head and neck (including gums, lips) are usual sites of predilection too. These cancers often grow in areas with scars from burns, chronic wound ulcers, injury from heat, as well as long-standing skin lesions such as discoid lupus erythematosus, osteomyelitis, etc.
Arsenic in drinking water, which is found naturally in certain parts of the world such as Bangladesh, Argentina, Chile, Taiwan and some parts in the United States, are associated with the development of non-melanoma skin cancers. Exposure to arsenic may be from toxic wastes, such as the infamous mine tailings spill in Marinduque, Philippines back in 1996. Other chemicals associated with the development of skin cancers include pesticides, asphalt, tar and polycyclic aromatic hydrocarbons
Human Papillomavirus(HPV) infection
Human papillomavirus, including those that cause common warts, are implicated in the development of SCC, especially in the anogenital region, more so in persons with HIV. While HPV vaccines against cervical cancer are already available, a vaccine that targets the prevention of skin cancer is still underway.
Most skin cancers are more common in the middle-aged to elder population but the most deadly type of skin cancer, melanoma, is more common in adolescents and young adults.
A previous history of skin cancer will raise the risk of developing another one. Having a close blood relative with skin cancers also raises one’s risk. Taking immunosuppressive drug to treat certain medical conditions or to prevent transplant rejection is another risk factor. Long-term exposure to x-rays or UV light treatment may also up the risk.
Prevention and early detection
The most straightforward prevention strategy is diligent sun protection, through regular (daily) use of sunscreens and other sun protective measures. A large prospective randomized controlled trial in Australia compared daily use of sunscreen vs. “discretionary” use for 15 years. At the end of the trial, they found a 50% reduction of melanoma incidence in the “daily” group, and an even bigger reduction (73%) in invasive melanoma[iv].
Avoidance of other risk factors such as environmental toxins, prompt management of skin ulcers or any skin irritation in general are important preventive measures
Early detection is key. Everyone should do a regular thorough monitoring of the skin. Those with more than 50 moles on their body should pay close attention for any changes in the skin. The American Academy of Dermatology has created a mole map to help people examine their skin and keep track of them over time (http://www.aad.org/dermatology-a-to-z/diseases-and-treatments/m—p/melanoma/tips). The danger signs are summed up as ABCDE – Asymmetry, Border (irregular), Color (varied), Diameter (bigger than a pencil eraser), and Evolving (changing in size, shape or color).
For Asians and Africans, it is very important to check the palms, soles, fingers, toes, nails, and the genital and oral mucosa because these are the usual sites for acral lentiginous melanoma, the variant that is most common in these populations. This subtype is considered as very aggressive and early detection provides the best chance for survival
Any skin lesion (not just moles) that shows enlargement, bleeding, crusting, ulceration, or redness are best evaluated by a trained (board-certified) dermatologist.
[i] Gloster HM and Neal K. Skin Cancer in Skin of Color. J Am Acad Dermatol 2006;55:741-60
[ii] Jean L. Bolognia, MD, Joseph L. Jorizzo, MD and Julie V. Schaffer, MD (eds). Dermatology, 3rd ed. Ed .Elsevier,2012
[iii] Adao-Grey AL. Profile of malignant skin tumors at UERMMMC. UERMMMC (University of the East Ramon Magsaysay Memorial Medical Center) Journal of Health Sciences July 1998; 1:1: 36-40
[iv] Green AC et al. Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow – Up. Journal of Clinical Oncology, Vol. 29 no. 3, pp 257-263 (2011)