The most common form of skin cancer is basal cell carcinoma or basal cell skin cancer. Basal cell carcinomas usually start as small lumps that gradually get bigger over time. The edges are often shiny or pearly and the middle tends to be rather sunken in or depressed. After some time the middle will start to become crusty and develop into an ulcer. Basal cell carcinomas do not usually cause any pain or discomfort, however they can be rather itchy.