Cancer develops when DNA, the molecule found in cells that encodes genetic information, becomes damaged and the body cannot repair the damage. These damaged cells begin to grow and divide uncontrollably. When this occurs in the skin, skin cancer develops. As the damaged cells multiply, they form a tumour. Since skin cancer generally develops in the epidermis, the outermost layers of skin, a tumour is usually clearly visible. This makes most skin cancers detectable in the early stages.
Causes of Skin Cancer
Sun exposure is the leading cause of skin cancer. Many of the more than 100,000 skin cancers diagnosed each year could be prevented with protection from the sun’s rays. Scientists now know that exposure to the sun’s ultraviolet (UV) rays damages DNA in the skin. The body can usually repair this damage before gene mutations occur and cancer develops. When a person’s body cannot repair the damaged DNA, which can occur with cumulative sun exposure, cancer develops.
Types of Skin Cancer
The different types of skin cancer are:
Accounting for about 4% of all diagnosed skin cancers, melanoma begins in the melanocytes, cells within the epidermis that give skin its colour. Melanoma has been coined “the most lethal form of skin cancer” because it can rapidly spread to the lymph system and internal organs. In the United States alone, approximately one person dies from melanoma every hour. Older Caucasian men have the highest mortality rate. Dermatologists believe this is due to the fact that they are less likely to heed the early warning signs. With early detection and proper treatment, the cure rate for melanoma is about 95%. Once it spreads, the prognosis is poor. Melanoma most often develops in a pre-existing mole or looks like a new mole, which is why it is important for people to know what their moles look like and be able to detect changes to existing moles and spot new moles.
Basal Cell Carcinoma (BCC):
The most common cancer in humans, BCC develops in more than 1 million people every year in the United States alone. About 80% of all skin cancers are BCC, a cancer that develops in the basal cells – skin cells located in the lowest layer of the epidermis. BCC can take several forms. It can appear as a shiny translucent or pearly nodule, a sore that continuously heals and then re-opens, a pink slightly elevated growth, reddish irritated patches of skin, or a waxy scar. Most BCCs appear on skin with a history of exposure to the sun, such as the face, ears, scalp, and upper trunk. These tumours tend to grow slowly and can take years to reach 1⁄2 cm in size. While these tumours very rarely metastasize (cancer spreads to other parts of the body), dermatologists encourage early diagnosis and treatment to prevent extensive damage to surrounding tissue.
Squamous Cell Carcinoma (SCC):
16% of diagnosed skin cancers are SCC. This cancer begins in the squamous cells, which are found in the upper layer of the epidermis. About 200,000 cases are diagnosed ever year. SCC tends to develop in fairskinned middle-aged and elderly people who have had long term sun exposure. It most often appears as a crusted or scaly area of skin with a red in amed base that resembles a growing tumour, non-healing ulcer, or crusted over patch of skin. While most commonly found on sun exposed areas of the body, it can develop anywhere, including the inside of the mouth and the genitalia. SCC may arise from actinic keratoses, which are dry, scaly lesions that may be skin-coloured, reddish-brown or yellowish-black. SCC requires early treatment to prevent metastasis (spreading).
Other non melanoma skin cancers:
All other skin cancers combined account for less than 1% of diagnosed cases. These are classified as non melanoma skin cancers and include Merkel cell carcinoma, dermato bromasarcoma protuberans, Paget’s disease and cutaneous T-cell lymphoma.
Who gets skin cancer?
Skin cancer develops in people of all colours, from the palest to the darkest. However, skin cancer is most likely to occur in those who have fair skin, light-coloured eyes, blonde or red hair, a tendency to burn or freckle when exposed to
the sun, and a history of sun exposure. Anyone with a family history of skin cancer also has an increased risk of developing skin cancer. In dark-skinned individuals, melanoma most often develops on non-sunexposed areas, such as the foot, underneath nails, and on the mucous membranes of the mouth, nasal passages, or genitals. Those with fair skin also can have melanoma develop in these areas.
Where on the body should you look for skin cancer?
Cancer Research UK has produced below illustration for men and women.
Skin cancer rates rising
While we now recognize that overexposure to the sun is unhealthy, the fact remains that most people do not protect their skin from the sun’s harmful rays. More than 100,000 non melanoma skin cancers are diagnosed each year, and there were 638 deaths from non-melanoma skin cancer in 2012.
If current trends continue, 1 in 5 will develop skin cancer during their lifetime. Melanoma continues to rise at an alarming rate. In 1930, 1 in 5,000 was likely to develop melanoma during their lifetime. By 2004, this ratio jumped to 1 in 65. Today, melanoma is the second most common cancer in women aged 15 to 34 and affects 21 in 100 000 people.
Prevention and early detection is the key
Sun protection can significantly decrease a person’s risk of developing skin cancer. Sun protection practices include staying out of the sun when the rays are strongest, applying a broad-spectrum (UVA and UVB protection) sunscreen with a Sun Protection Factor (SPF) of 30 or higher year-round to all exposed skin, and wearing protective clothing, such as a wide-brimmed hat and sunglasses when outdoors.
Since skin cancer is so prevalent today, dermatologists and plastic surgeons also recommend that everyone learns how to recognise the signs of skin cancer, use this knowledge to perform regular examinations of their skin, and see a skin expert annually (more frequently if at high risk) for an examination. Skin cancer is highly curable with early detection and proper treatment.