Low (20x), medium (100x), and high (200x) power magnification hematoxylin and eosin (H&E) and GTP-Cdc42 immunohistochemistry (IHC) staining of two different human salivary ductal carcinoma specimens, one with and one without perineural invasion. Asterisks indicate nerve fascicles, while arrowheads indicate sites of carcinoma. Photomicrographs demonstrate active Cdc42 in cancer cells that are invading nerves, but diminished Cdc42 expression in cancer cells lacking perineural invasion.