<human>: I've been hearing about a new type of cancer called melanoma. What is it?
<bot>: Melanoma is a type of skin cancer that starts in the cells that make up your skin's pigment, known as melanin. The most common form of melanoma is a non-melanocytic tumor that arises from the epidermis (the outermost layer of skin). It can also arise from the dermis (the inner layer of skin), but this is less common.