Schematic representation of the genomic alterations detected in peripheral blood cells (b) and tumors (t) from the parents and twins. In peripheral blood, loss of 9p13.1-p12 was the unique novel CNV shared by the twins. Two specific CNVs mapped in chromosome X were shared by both tumor and blood samples of each sibling, including Xq28 for Twin-1 and Xq27.3 for Twin-2. The panel of novel CNVs shared by embryonal carcinoma (Twin-1 t) and the seminoma (Twin-2 t), including gains at 12p (12p12.3-p11.1 and 12p13.33-p12.3), as well as losses at 10p15.3-p15.2, 13q21.1-q21.2 and 15q11.1-q11.2. None of these novel CNVs were shared with the parental genotypes.