Skin cancer consists of the growth of abnormal skin cells which don't respect their normal functions and cycles. As in other types of cancers, these cells tend to grow and multiply, and they destroy surrounding tissues and eventually depart from or invade their original group of cells, and do the same on other parts of the body (metastasis).

Skin cancer is the most common type of cancer in humans. There are more cases of skin cancer than the number of cases of all other cancers combined.

Skin cancer is so common nowadays, that the Skin Cancer Foundation estimates that:

• 1 in 5 Americans will develop skin cancer before they reach the age of 70;
• More than 2 persons per hour die of skin cancer in the USA;
• 5 or more UV ray burns doubles the risk of developing melanoma;
• When treated on time, 99% of people affected with melanoma live more than 5 years;

Causes for skin cancer

The circumstances or elements from the environment that affects skin cells and their genetic code are:

• Over-exposure to UV radiation (i.e. sun, solar beds).
• Radiotherapy (i.e. X rays, Gamma rays Gamma used to treat cancer).
• Continuous exposure to toxic chemicals such as arsenic.
• Immunosuppressive medications.
• Diets that are low in antioxidants.

Risk Factors

One of the best-known risk factors contributing to the development of skin cancer is overexposure to UV rays from the sun, age, and light tone of the skin. Elder people with light skin tone have a high risk of developing basal cell carcinoma. Some parts of the planet where the temperature tends to be high and skin tone tends to be light (i.e. Australia), have the highest proportion of skin cancer in the world. Northern Europeans also have a high risk due to their light skin tone.

Skin cancer tends to develop the most in those areas usually exposed to the sun, such as the face. Skin cancer may also develop in other parts of the head and neck, and only 20% of the time they may develop in areas least exposed to the sun such as the chest, back, limbs, or scalp.

Types of proliferative lesions of the skin

Proliferative lesions of the skin may be benign or malignant. Benign lesions are also known as pre-malignant lesions due to their risk of becoming malignant if left untreated. Almost all malignant or pre-malignant lesions are associated with exposure to UV radiation.

Benign or pre-malignant skin lesions can be classified as pigmented (they have a normal colour) or unpigmented (they have excess melanin or dark colour.

The most common pigmented lesions are freckles, age spots or solar lentigo, and moles. Normally these lesions have a uniform color, flat in the case of freckles and lentigo, or raised and with even borders in the case of moles.

The most common unpigmented lesions are warts, amelanotic moles, and epidermoid cysts.

Other benign skin lesions are the different types of keratosis. These are proliferative lesions of keratinocytes, which are the cells that form the most superficial part of the skin or keratin. Most common type of keratosis is actinic or solar keratosis, a pre-malignant lesion that can degenerate into squamous cell in up to 10% of cases. Keratosis lesions are pretty common and, in some countries, it can affect up to 50% of elderly people.

Given the high incidence of actinic keratosis, it is convenient to treat these lesions to avoid the possibility of them degenerating into squamous cell carcinoma. There are many available treatments for actinic keratosis and usually, they are the same applied for skin cancers.

Prevention

According to the Skin Cancer Foundation, skin damage due to exposure to UV rays is cumulative. Nearly 23 % of the damage to the skin due to exposure to the sun in humans occurs before reaching the age of 18.

Regular use of sunscreens with grade 15 or more, reduces the risk of developing a squamous cell carcinoma in approximately 40%.

Diagnosis

Skin cancer diagnosis is established under the microscope, examining a sample obtained through biopsy or excision of the lesion. Depending on the type, skin cancer is relatively easy to treat with early detection. Also, there are in developing artificial intelligence applications that allow a high degree of accuracy in diagnosing images of skin lesions.

Treatments for skin cancer

• Excision (surgery). The medical professional excises (cuts out) the cancerous tissue and a surrounding margin of healthy skin.
• Mohs surgery. The medical professional removes the skin growth layer by layer, examining each layer under the microscope, until no abnormal cells remain. This procedure allows cancerous cells to be removed without taking an excessive amount of surrounding healthy skin.
• Freezing. Medical professional applies liquid nitrogen (cryosurgery) to freeze and destroy actinic keratoses and some small, early skin cancers. The dead tissue sloughs off later on.
• Curettage and cryotherapy. Medical professional removes most of a growth, and scrapes away layers of cancer cells with a curet. He uses an electric needle to destroy remaining cancer cells.
• Radiation therapy. Used when cancerous cells can't be completely removed during surgery. A medical doctor applies high-powered energy beams, such as X-rays, to kill cancer cells.
• Chemotherapy. Consists of the use of drugs to kill cancer cells. For cancers limited to the top layer of skin, creams or lotions containing anti-cancer agents may be applied directly to the skin. Systemic chemotherapy can be used to treat skin cancers that have spread to other parts of the body.
• Photodynamic therapy. This treatment destroys skin cancer cells with a combination of laser light and drugs that makes cancer cells sensitive to light.
• Biological therapy. Biological therapy uses your body's immune system to kill cancer cells. Improvement of the immune system works its way out up to the cancerous cells and treats the skin cancer. Treatment products containing Imiquimod (Aldara, Zyclara, Interferon) are used for this purpose.
• Natural therapy. Active compound BEC (based on eggplant) works its way to the endo-lectins of the cancerous cells and causes their apoptosis (death). Treatment products containing BEC for skin cancer and actinic keratosis are Curaderm BCC, among others. BEC is a group of natural compounds extracted from the eggplant family of plants (Solanaceae). Dr. Bill E. Cham discovered it in the late 70s at the University of Queensland in Australia. When investigating on Australian ranchers' folklore that mentioned of improvement in their cattle cancers by applying a poultice made from a local fruit belonging to the family of the eggplant: Solanum linnaeanum. From this plant, BEC was extracted and purified. There exist several publications of clinical trials using BEC in a topical formulation for the treatment of proliferative skin lesions, such as BCCs.

References

1. Skin Cancer Facts & Statistics on Skin Cancer Foundation (skincancer.org)
2. Sympthoms of skin cancer on CuradermBCC.eu
3. Actinic Keratosis on Wikidoc.org