6) Viral infections:
Certain viruses may induce genetic mutations and lead to the formation of skin cancer. That is the case of certain strains of human papillomavirus and human herpesvirus 8 in immunocompromised patients.
As noted above, sun exposure is probably the most commonly accepted cause of cancer but not the only one. If sun exposure were the sole cause, it would not be possible to explain cancer found in non-exposed areas, such as the feet and lower back. However, exposed or not, some patients may still develop skin cancer, and the majority of them have a family history of melanoma or any other variant. Thus, it is essential to inspect all of your skin if you’re looking for skin cancer, including areas that are not always exposed to the sun. Keep in mind that suppression of the immune system due to any cause may lead to skin cancer as well, so do not neglect any worrying sign or symptom and go to the doctor if you have any doubt.