Acancer or cancerous tumour on the skin
as a result of extensive exposure to uv rays.

Almost all skin cancers (approximately 99% of non-melanoma skin cancers and 95% of melanoma) are caused by too much UV radiation from the sun or other sources such as solaria (solarium, sunbeds, and sun lamps).  

Explanation:

Skin cancer develops in the cells in the epidermis – the top or outer layer of the skin.  UV radiation is made up of UVA and UVB rays which are able to penetrate the skin and cause permanent damage to the cells below:

UVA penetrates deeply into the skin (the dermis) causing genetic damage to cells, photo-ageing (wrinkling, blotchiness etc) and immune-suppression.

UVB penetrates into the epidermis (top layer of the skin) causing damage to the cells. UVB is responsible for sunburn – a significant risk factor for skin cancer, especially melanoma.

If the body is unable to repair this damage the cell can begin to divide and grow in an uncontrolled way. This growth can eventually form a tumor.

UVA and UVB both contribute to sunburn, skin ageing, eye damage and melanoma and other skin cancers.

probably not if net force is zero