There are three main types of skin cancer:
Basal cell carcinoma is the most common type, and it is also the easiest to treat. It typically only affects the top layers of skin and does not spread to the blood or lymph nodes.
Squamous cell carcinoma can involve the middle layers of skin as well, and it can spread in the lymph nodes or blood, or grow into deeper tissues like bone.
Melanoma is the most serious type. It carries the greatest risk for spread and can affect the body's organs and systems away from the original skin cancer site.