KCNJ13 and choroid plexus neoplasm: Immunohistochemical detection of Kir7.1, an inwardly rectifying potassium channel that has been shown to be a marker for human choroid plexus tumors, will stain the apical portion of neoplastic choroid plexus cells in the dog and can be used as a specific marker to differentiation choroid plexus tumor origin from other carcinomas that may have metastasized to the central nervous system (Figure 3F) (147).