Finally, it is important to note that there is a statistically significant correlation between the frequency of cytosine-phosphate-guanine island methylation in the 5' upstream non-coding region of the Ecrg4 gene and the degree of malignancy in several types of cancers, including choroid plexus papillomas and carcinoma [16,18,50]. Here, ECRG4 is linked to choroid plexus papilloma.