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Skin cancer

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Skin cancer is a condition where abnormal cells grow uncontrollably within the skin. These cells form malignant tumors, which are growths that can invade nearby tissue. They may also spread to other parts of the body. Skin cancer is the most common form of cancer in humans. Globally, it accounts for at least 40% of all cancer cases.

Melanoma and other skin cancers world map - Death - WHO2004
Melanoma and other skin cancers world map - Death - WHO2004

The primary cause of these cancers is exposure to ultraviolet (UV) radiation. This radiation comes from the sun or from artificial tanning devices. UV radiation causes damage to the DNA inside skin cells through photochemical reactions. Specifically, it can form cyclobutane pyrimidine dimers between adjacent bases in the DNA. While human cells use a process called nucleotide excision repair to fix this damage, high levels of exposure can overwhelm this system.

Melanoma - cytology field stain
Melanoma - cytology field stain

There are three main types of skin cancer. The first is basal-cell carcinoma (BCC), which is the most common. It often appears as a shiny, raised, pearly bump on sun-exposed areas like the face. BCC grows slowly and rarely spreads to distant areas. The second type is squamous-cell carcinoma (SCC). This often presents as a hard, red, or scaly patch. SCC is more likely to spread than BCC, especially in the lip or ear.

Basal cell carcinoma3
Basal cell carcinoma3
Squamous Cell Carcinoma1
Squamous Cell Carcinoma1

The third and most aggressive type is melanoma. Melanomas can develop from existing moles, which accounts for 20% to 30% of cases. They are often characterized by irregular shapes, colors, and borders. Doctors use the "ABCDE" mnemonic to identify warning signs. This stands for asymmetry, irregular borders, color variation, diameter larger than 6 mm, and evolving size or shape.

Melanoma
Melanoma

Different types of UV radiation affect the skin in different ways. BCC and SCC often carry a UV-signature mutation. This indicates they are caused by UVB radiation through direct DNA damage. In contrast, melanoma is predominantly caused by UVA radiation. This type of damage is indirect and is caused by free radicals and reactive oxygen species. Exposure to UV radiation has increased since the Industrial Revolution, partly due to ozone depletion.

Melanoma
Melanoma

Risk factors vary depending on the individual and the type of cancer. People with lighter skin or poor immune function are at higher risk. For example, certain medications like cyclosporin A can increase risk significantly. For melanoma and BCC, exposure during childhood is particularly harmful. However, for SCC, total lifetime exposure is the more important factor.

Melanoma
Melanoma

Diagnosis is usually confirmed through a biopsy. This is a procedure where a doctor removes a sample of tissue for examination. There are also non-invasive methods like dermatoscopy and various types of spectroscopy. Once diagnosed, treatment depends on the type of cancer. Nonmelanoma skin cancers are usually curable through surgical removal or radiation. Melanoma treatment may require a combination of surgery, chemotherapy, and targeted therapy.

Melanoma
Melanoma

Survival rates for melanoma are relatively high compared to other cancers. In the United States, more than 90% of people survive for at least five years. In the United Kingdom, the survival rate is over 86%. However, melanoma remains serious because it can cause death once it spreads. In 2012, melanoma affected 232,000 people globally and resulted in 55,000 deaths.

Melanoma and other skin cancers world map - Death - WHO2004
Melanoma and other skin cancers world map - Death - WHO2004
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🖼️ Images & Media (5)
File:Basal cell carcinoma3.JPG
Basal cell carcinoma3.JPG
File:Squamous Cell Carcinoma1.jpg
Squamous Cell Carcinoma1.jpg
File:Melanoma.jpg
Melanoma.jpg
File:Melanoma - cytology field stain.jpg
Melanoma - cytology field stain.jpg
File:Melanoma and other skin cancers world map - Death - WHO2004.svg
Melanoma and other skin cancers world map...
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