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.