Case study 127 - Choroid Plexus Papilloma Choroid plexus papilloma (CPP) is a rare type of brain tumor. It’s generally slow growing and not cancer (benign). Benign also means that the growth doesn’t spread to other parts of the body. CPP is most common in young children, but it can also appear in adults. A CPP tumor grows in the choroid plexus. This is a layer of tissue within the brain that makes the cerebrospinal fluid (CSF). In adults, CPP tends to form in the fourth ventricle. In children, i