In fact, IPN genes from these overrepresented families are included in the four main families of axon guidance cues and receptors (ephrins/Ephs, Netrins/DCC-Unc5, Semaphorins/Neuropilins-Plexins, and Slits/ROBO), evidence of the importance of axon guidance mechanisms at this stage of IPN development. The gene discussed is DCC; the disease is bile duct papillary neoplasm.