PTCH1 and neoplasm: In agreement with previous reports, 24/28 informative tumors showed a co-occurring PTCH1 biallelic inactivation including a large 9q deletion encompassing both ELP1 and PTCH1 loci, confirming that the “four hit-three steps” model is the rule for these MB; 1 single PTCH1 alteration was found for the 4 remaining tumors, one of which also showed a heterozygous SUFU inactivating PV; finally, for 1 tumor, ELP1 sequence and MYCN FISH results were the only available biological characteristics.