Despite sharing common chromosomal alterations, these groups can be further differentiated by subclass-specific changes: platelet-derived growth factor receptor α (PDGFRA) amplification in RTK I, gain of chromosomes 19 and 20 in RTK II, and neurofibromin 1 (NF1) mutations in MES tumors [3,6,7]. The gene discussed is NF1; the disease is Meckel syndrome, type 1.