Monday, August 30, 2010
Skin Cancer Caused by the Sun
The ability of the sun to cause skin cancer is a well-known fact. The 3 main skin cancers are melanoma, basal cell carcinoma, and squamous cell carcinoma. Melanoma is the most deadly skin cancer because it metastasizes more readily than the other skin cancers. It is believed that the amount of exposure of the skin to the sun before the age of 20 is actually the determining risk factor for melanoma. Basal cell carcinoma is the most common skin cancer and tends to spread locally, not metastasize. Squamous cell carcinoma is the second most common skin cancer, and it can metastasize although not as commonly as melanoma. The risk of getting basal cell carcinoma or squamous cell carcinoma is determined by a person's lifetime exposure to UV radiation and the person's pigment protection
UV exposure causes thickening and thinning of the skin. Thick skin is found in coarse wrinkles especially on the back of the neck that do not disappear when the skin is stretched. A condition called solar elastosis is seen as thickened, coarse wrinkling and yellow discoloration of the skin. A common effect of UV exposure is thinning of the skin causing fine wrinkles, easy bruising, and skin tearing.
UV radiation causes the walls of blood vessels to become thinner leading to bruising
With only minor trauma in sun-exposed areas. For example, most of the bruising that occurs on sun-damaged skin occurs on the backs of the hands and forearms not on the inside of the upper arm or even the inside of the forearm. The sun also causes the appearance of telangiectasias, tiny blood vessels, in the skin especially on the face
Pigment Changes Caused by the Sun:
The most noticeable sun-induced pigment change is a freckle or solar lentigo. Light-skinned people tend to freckle more noticeably. A freckle is caused when the melanin-producing cell, or melanocyte, is damaged causing it to get bigger. Large freckles, also known as age spots or liver spots, can be seen on the backs of the hands, chest, shoulders, arms, and upper back. These are not actually age related but sun-damage related. UV exposure can also cause white spots especially on the legs, but also on the backs of the hands and arms, as melanocytes are destroyed.