Exposure to ultraviolet (ultraviolet A and B) or ionizing radiation:
(1) excessive sun exposure, especially with actinic keratosis
(2) therapy with methotrexate and ultraviolet A radiation
(3) radiation therapy
(4) chronic exposure to a radiation source, especially with radiation induced dermatitis or keratoses
Exposure to chemical carcinogens and heavy metals:
(1) arsenic, especially with arsenical keratosis
(2) polycyclic aromatic hydrocarbons
Genetic disorders:
(1) genodermatosis
(2) oculocutaneous albinism
(3) xeroderma pigmentosum
Infections:
(1) human papillomavirus, especially types 6, 11, 16 and 18
Chronic injury and/or inflammation (see Marjolin Ulcers, below):
(1) a longstanding dermal ulcers
(2) chronic osteomyelitis
(3) a chronic sinus tracts
(4) dystrophic epidermolysis bullosa
Immunosuppression:
(1) organ transplantation
(2) leukemia and lymphoma
(3) immunosuppressive medications
