re skin cancer

Mon Feb 6 07:16:13 EST 1995

With regard to UV as a cause of skin cancer the first things to note
are that there are several skin cancers (squamous cell carcinoma, basal
cell carcinoma, malignant melanoma, Kaposi's sarcoma & others). Also cancer
does not usually have a single cause but has several factors which
increase the risk of the disease (predisposing factors). So although
UV has been linked with skin malignancies it is not THE cause. Many
people get exposed to UV without developing the malignacies and other
agents (such as chemical carcinogens, genetic predisposition) may be
more important in some cases.

UV has been linked with both squamous cell carcinoma and basal cell
carcinoma. The exposure in this case seems to be chronic exposure.
They occur in exposed areas of skin in older people who have a history
of outdoor occupations.

Malignant melanoma is also linked to UV but shows a different pattern.
It occurs in a younger age group and is associated with indoor workers
who get burnt by the sun rather than developing a slow tan. The burning
is most dangerous in the young (<15 year old) though the disease may not
appear for 10-20 years.

The UV damage seems to be a direct effect on the DNA in the skin cells
and causes adjacent thymines in the DNA to become dimerised. This causes
a distortion in the DNA which can be corrected by DNA repair enzymes.
Defective repair is found in the disease Xeroderma pigmentosum and
patients with this rare disease show an increased incidence of skin tumours.

Kaposi's sarcoma does not seem to be linked with exposure to UV but is 
instead linked with AIDS.

I hope this helps. If you need any other information try any good pathology
book or ONCOLINk on the WWW ( )

John Cook

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