A tumor is tissue which grows at a time and in a location of the body where it is not supposed to grow. Like all tissues, a tumor is made of cells. These cells share many characteristics with normal body cells, from which they probably arise. Tumor cells, however, differ from normal cells in that they keep proliferating even when this is not beneficial for the remainder of the organism. Regulatory mechanisms which stop proliferation in normal cells are not functioning enough in tumor cells, while mechanisms making them grow are over-active. Various tumor types comprise a large spectrum with regards to how much they differ from normal cells. At one end of the spectrum are benign tumors. In general, these tumor cells closely resemble certain types of normal cells. They grow slowly, do not infiltrate surrounding normal tissue, and they stay in the place of their origin. At the other end of the spectrum is the malignant tumor, which is also called ‘cancer’. These tumor cells proliferate quickly, infiltrate normal tissue, and can separate from the normal tumor, adhere in a different place of the body, continue to grow there and form a second tumor in this place. These distant tumors are called ‘metastases’.

    Choroid plexus is normal tissue in the brain which produces cerebral spinal fluid ("CSF"). It is located in normal fluid spaces at the centre of the brain, which are called ‘ventricles’. There is a lateral ventricle on the right, and one on the left, as well as a third and a fourth ventricle at the middle of the brain. The cerebral spinal fluid is a clear, water-like fluid which slowly flows from the lateral to the third and then to the fourth ventricle, after which it leaves the middle of the brain to be reabsorbed in the tissue surrounding the central nervous system. Tumors arising from the choroid plexus are called ‘choroid plexus papilloma’ when they are relatively benign, or ‘choroid plexus carcinoma’ when they are more malignant.

    There are four main groups of causes which are discussed in cancer research: inherited susceptibility for cancer, radioactivity, chemicals, and viruses. With respect to choroid plexus tumors, a link has been described to a familial syndrome called Li-Fraumeni syndrome. In those families, breast cancer, sarcoma, leukemia, and other brain tumors are more frequent. It is caused by an alternation of the p53 gene. In addition, there is experimental evidence that the Simian virus 40 (SV40) can cause choroid plexus tumors in animals. This virus is otherwise harmless to humans and it is still not clear if it can really cause choroid plexus tumors in humans.

    This type of tumor is very rare. Exact numbers are not known. However, it can be estimated that 1,500 new tumors of this type occur in the world per year. Most of these tumors occur in infants, but they can occur at any age. The exact distribution and frequency is unknown. The international study attempts to create more reliable data to clarify these points.

    Yes - if there were no treatment, a fatal outcome from the disease is most likely. But this tumor can be treated, and the treatment will quite frequently be successful. The likelihood of a successful outcome depends on many variables, such as the age of the patient, the location and size of the tumor, the presence or absence of Li-Fraumeni syndrome, and whether or not the tumor has already spread (metastasized). Overall, about half of the patients survive for 10 or more years after the diagnosis, which comes close to a cure from the tumor disease. The two most important factors which determine whether or not an individual will be in the group of survivors, are the microscopic picture of the tumor (benign or malignant, papilloma or carcinoma), and if the tumor could be completely surgically removed. Patients who have choroid plexus papilloma, which can be completely removed, have an excellent prognosis when compared to other tumor diseases. In most of these patients, the tumor will not recur, and even with recurrence, it might still be possible to treat successfully. On the other end of the spectrum are patients with choroid plexus carcinoma, which cannot be surgically removed and have already metastasized. Without further treatment such as irradiation and chemotherapy, these patients will most likely die. The CPT-SIOP-studies are meant to standardize and improve the treatment of choroid plexus tumors so that the overall outcome will be better in the future.