To perform a skin biopsy, your dermatologist first numbs the area with an injection. Once the area is numb, your provider removes some (or all) of the growth. This is sent to a lab, where a dermatopathologist or a board certified dermatologist will examine the specimen under a microscope. A dermatopathologist is a dermatologist who receives specialized training in examining skin samples. Many rashes that cannot be diagnosed with the naked eye can be better investigated with a biopsy. The only way to know for certain whether a growth is skin cancer is to examine it this way under a microscope.