Saturday, 6 October 2012

Skin cancer, skin cancer disease,


Skin neoplasms (also known as "skin cancer") are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancersquamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises..
Skin cancer generally develops in the epidermis (the outermost layer of skin), so a tumor can usually be seen. This means that it is often possible to detect skin cancers at an early stage. Unlike many other cancers, including those originating in the lungpancreas, and stomach, only a small minority of those affected will actually die of the disease, though it can be disfiguring. Melanoma survival rates are poorer than for non-melanoma skin cancer, although when melanoma is diagnosed at an early stage, treatment is easier and more people survive.
Skin cancer is the most commonly diagnosed type of cancer. Melanoma and non-melanoma skin cancers combined are more common than lungbreastcolorectal, and prostate cancer. Melanoma is less common than both basal cell carcinoma and squamous cell carcinoma, but it is the most serious — for example, in the UK there were over 11,700 new cases of melanoma in 2008, and over 2,000 deaths.59,695 people in the United States were diagnosed with melanomas of the skin, including 38,484 men and 25,211 women. 8,623 people in the United States died from melanomas of the skin, including 5,672 men and 2,951 women.
It is the second most common cancer in young adults aged 15–34 in the UK.Most cases are caused by over-exposure to UV rays from the sun or sunbeds. Non-melanoma skin cancers are the most common skin cancers. The majority of these are basal cell carcinomas. These are usually localized growths caused by excessive cumulative exposure to the sun and do not tend to spread.

Basal cell carcinomas are present on sun-exposed areas of the skin, especially the face. They rarely metastasize and rarely cause death. They are easily treated with surgery or radiation. Squamous cell carcinomas (SCC) are common, but much less common than basal cell cancers. They metastasize more frequently than BCCs. Even then, the metastasis rate is quite low, with the exception of SCC of the lip, ear, and in immunosuppressed patients. Melanomas are the least frequent of the 3 common skin cancers. They frequently metastasize, and could potentially cause death once they spread.
Less common skin cancers include: Dermatofibrosarcoma protuberansMerkel cell carcinomaKaposi's sarcomakeratoacanthoma, spindle cell tumors, sebaceous carcinomas, microcystic adnexal carcinoma, Pagets's disease of the breast, atypical fibroxanthoma, leimyosarcoma, and angiosarcoma.
The BCC and the SCCs often carry a UV-signature mutation indicating that these cancers are caused by UV-B radiation via the direct DNA damage. However the malignant melanoma is predominantly caused by UV-A radiation via the indirect DNA damage.The indirect DNA damage is caused by free radicals and reactive oxygen species. Research indicates that the absorption of three sunscreen ingredients into the skin, combined with a 60-minute exposure to UV, leads to an increase of free radicals in the skin, if applied in too little quantities and too infrequently. However, the researchers add that newer creams often do not contain these specific compounds, and that the combination of other ingredients tends to retain the compounds on the surface of the skin. They also add the frequent re-application reduces the risk of radical formation.

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.

Causes

Ultraviolet radiation from sun exposure is the primary cause of skin cancer.Other factors that play a role include:
  • 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, 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 basil and squamous cell carcinomas.

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 periods of peak sun exposure.The U.S. Preventive Services Task Force recommends that people aged between 9 and 25 years of age are 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 and increasing the use of sunscreen.Avoiding the use of tobacco products
There is insufficient evidence to recommend for or against screening for skin cancer.Vitamin supplements and antioxidant supplements have not been found to have an effect in prevention. Evidence for a benefit from dietary measures is tentative.



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