BCL2 and post-transplant lymphoproliferative disease: Comparative genomic hybridization analysis has confirmed the occurrence of these alterations and has shown that PTLD is characterized by distinct genetic aberrations (losses of 4q, 17q, and Xp) as well as changes that are also common in lymphoma arising in immunocompetent patients but with different frequencies (losses of 1p, 6q, 9p, 17p13: TP53; gains of 3q27: BLC-6, 5p, 7q, 8q24: C-MYC, 11p, 12q, 12p, 18q21: BCL-2 and MALT, and 21q) [21].