Skin Cancer

Skin cancer

These are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. 

Types Skin cancer

There are three main types of skin cancers: 

1. Basal-cell skin cancer (BCC), 
2. Squamous-cell skin cancer (SCC) and 
3. Melanoma. 

The first two, along with a number of less common skin cancers, are known as nonmelanoma skin cancer (NMSC). Basal-cell cancer grows slowly and can damage the tissue around it but is unlikely to spread to distant areas or result in death. It often appears as a painless raised area of skin, that may be shiny with small blood vessel running over it or may present as a raised area with an ulcer. Squamous-cell cancer is more likely to spread. It usually presents as a hard lump with a scaly top but may also form an ulcer. Melanomas are the most aggressive. Signs include a mole that has changed in size, shape, color, has irregular edges, has more than one color, is itchy or bleeds.

Greater than 90% of cases are caused by exposure to ultraviolet radiation from the Sun. This exposure increases the risk of all three main types of skin cancer. Exposure has increased partly due to a thinner ozone layer. Tanning beds are becoming another common source of ultraviolet radiation. For melanomas and basal-cell cancers exposure during childhood is particularly harmful. For squamous-cell cancers total exposure, irrespective of when it occurs, is more important. Between 20% and 30% of melanomas develop from moles. People with light skin are at higher risk as are those with poor immune function such as from medications or HIV/AIDS. Diagnosis is by biopsy.

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Signs and symptoms

There are a variety of different skin cancer symptoms. These include changes in the skin that do not heal, ulcering in the skin, discolored skin, and changes in existing moles, such as jagged edges to the mole and enlargement of the mole.

Basal-Cell Skin cancer

Basal-cell skin cancer (BCC) usually presents as a raised, smooth, pearly bump on the sun-exposed skin of the head, neck or shoulders. Sometimes small blood vessels (called telangiectasia) can be seen within the tumor. Crusting and bleeding in the center of the tumor frequently develops. It is often mistaken for a sore that does not heal. This form of skin cancer is the least deadly and with proper treatment can be completely eliminated, often without scarring.

Squamous-Cell Skin cancer

Squamous-cell skin cancer (SCC) is commonly a red, scaling, thickened patch on sun-exposed skin. Some are firm hard nodules and dome shaped like keratoacanthomas. Ulceration and bleeding may occur. When SCC is not treated, it may develop into a large mass. Squamous-cell is the second most common skin cancer. It is dangerous, but not nearly as dangerous as a melanoma.

Melanoma

Most melanoma consist of various colours from shades of brown to black. A small number of melanoma are pink, red or fleshy in colour; these are called amelanotic melanoma and tend to be more aggressive. Warning signs of malignant melanoma include change in the size, shape, color or elevation of a mole. Other signs are the appearance of a new mole during adulthood or pain, itching, ulceration, redness around the site, or bleeding at the site. An often-used mnemonic is "ABCDE", where A is for "asymmetrical", B for "borders" (irregular: "Coast of Maine sign"), C for "color" (variegated), D for "diameter" (larger than 6 mm—the size of a pencil eraser) and E for "evolving."

Other

Merkel cell carcinomas are most often rapidly growing, non-tender red, purple or skin colored bumps that are not painful or itchy. They may be mistaken for a cyst or another type of cancer.

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Causes

Ultraviolet radiation from sun exposure is the primary environmental cause of skin cancer. Other risk factors that play a role include:

• Smoking tobacco
• HPV infections increase the risk of squamous-cell carcinoma.
• Some genetic syndromes including congenital melanocytic nevi syndrome which is characterized by the presence of nevi (birthmarks or moles) of varying size which are either present at birth, or appear within 6 months of birth. Nevi larger than 20 mm (3/4") in size are at higher risk for becoming cancerous.
• Chronic non-healing wounds. These are called Marjolin's ulcers based on their appearance, and can develop into squamous-cell carcinoma.
• Ionizing radiation such as X-rays, environmental carcinogens, artificial UV radiation (e.g. tanning beds), aging, and light skin color. It is believed that tanning beds are the cause of hundreds of thousands of basal and squamous-cell carcinomas. The World Health Organization now places people who use artificial tanning beds in its highest risk category for skin cancer. Alcohol consumption, specifically excessive drinking increase the risk of sunburns.
• The use of many immunosuppressive medications increases the risk of skin cancer. Cyclosporin A, a calcineurin inhibitor for example increases the risk approximately 200 times, and azathioprine about 60 times.

• Prevention

  Sunscreen is effective and thus recommended to prevent melanoma and squamous-cell carcinoma. There is little evidence that it is effective in preventing basal-cell carcinoma. Other advice to reduce rates of skin cancer includes avoiding sunburning, wearing protective clothing, sunglasses and hats, and attempting to avoid sun exposure or periods of peak exposure. The U.S. Preventive Services Task Force recommends that people between 9 and 25 years of age be advised to avoid ultraviolet light.
  The risk of developing skin cancer can be reduced through a number of measures including decreasing indoor tanning and mid day sun exposure, increasing the use of sunscreen, and avoiding the use of tobacco products.
  There is insufficient evidence either for or against screening for skin cancers. Vitamin supplements and antioxidant supplements have not been found to have an effect in prevention. Evidence for a benefit from dietary measures is tentative.
  Zinc oxide and titanium oxide are often used in sun screen to provide broad protection from UVA and UVB ranges.
  Eating certain foods may decrease the risk of sunburns but this is much less than the protection provided by sunscreen.

  Treatment

  Treatment is dependent on type of cancer, location of the cancer, age of the person, and whether the cancer is primary or a recurrence. Treatment is also determined by the specific type of cancer. For a small basal-cell cancer in a young person, the treatment with the best cure rate (Mohs surgery or CCPDMA) might be indicated. In the case of an elderly frail man with multiple complicating medical problems, a difficult to excise basal-cell cancer of the nose might warrant radiation therapy (slightly lower cure rate) or no treatment at all. Topical chemotherapy might be indicated for large superficial basal-cell carcinoma for good cosmetic outcome, whereas it might be inadequate for invasive nodular basal-cell carcinoma or invasive squamous-cell carcinoma. In general, melanoma is poorly responsive to radiation or chemotherapy.
  For low-risk disease, radiation therapy (external beam radiotherapy or brachytherapy), topical chemotherapy (imiquimod or 5-fluorouracil) and cryotherapy (freezing the cancer off) can provide adequate control of the disease; all of them, however, may have lower overall cure rates than certain type of surgery. Other modalities of treatment such as photodynamic therapy, topical chemotherapy, electrodesiccation and curettage can be found in the discussions of basal-cell carcinoma and squamous-cell carcinoma.
  Mohs' micrographic surgery (Mohs surgery) is a technique used to remove the cancer with the least amount of surrounding tissue and the edges are checked immediately to see if tumor is found. This provides the opportunity to remove the least amount of tissue and provide the best cosmetically favorable results. This is especially important for areas where excess skin is limited, such as the face. Cure rates are equivalent to wide excision. Special training is required to perform this technique. An alternative method is CCPDMA and can be performed by a pathologist not familiar with Mohs surgery.
  In the case of disease that has spread (metastasized), further surgical procedures or chemotherapy may be required.
  Treatments for metastatic melanoma include biologic immunotherapy agents ipilimumab, pembrolizumab, and nivolumab; BRAF inhibitors, such as vemurafenib and dabrafenib; and a MEK inhibitor trametinib.