Predisposing factors for skin cancer are-a)  Smokingb)  U-V-light c)  Chronic ulcerd)  Infrared light
Exposure to Sun (UV rays) Major predisposing factors.                    o Old burn scars
Industrial carcinogens (Tars and oils)                                                    o Ingestion of arsenicals
Chronic ulcers and draining osteomyelitis.                                           o Ionizing radiation

Note : Cigarette smoking and tobacco & betel nut chewing are predisposing factors for squamous cell carcinoma of lips and oral cavity.
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