skin
These cancers would first appear on the skin.
skin
skin
skin
Ultraviolet radiation (part of sunlight).
Melanoma is a cancer of the skin. And the skin is technically a part of the integumentary system.
This type of mutation is known as a deletion.
Deletion
the final part of the body is foot
It would be as if a part of a chromosome were lost. This is called a deletion. It can cause a gene to be lost or not expressed. Several genetic disorders are caused by this process.
The same part that is the cleanest part of a man. Genitalia are, as a rule, full of natural bodily excretions. Which would mean that gender would not be relevant to the cleanest body part.