Dermatologists are trained in all four branches of dermatology, but they can choose to specialize in a particular branch. Medical: Diagnoses, treats, and prevents skin, hair, and nail diseases Surgical: Uses surgical procedures for treatment (such as removing skin cancer) Cosmetic: Focuses on improving the appearance of skin, hair, and nails, which may include injecting fillers Dermatopathology: Examines skin, hair, and nail samples with a microscope