MDM2 and atypical lipomatous tumor: The cytogenetic features of ALT/WDLPS are excess circular macrochromosomes containing amplified 12q13-15 sequences; amplification of MDM2 and CDK4 genes is the most constant in this region.[15–17] The human MDM2 gene is located in the 12q13-14 segment of the chromosome, which regulates cell cycle progression in the transition from the G1/S phase and controls the differentiation and proliferation of normal cells.[18] MDM2-encoded proteins can bind to the p53 protein and negatively regulate the p53 protein, thereby promoting tumorigenesis.[19] CDK4 regulates the G1/M cell cycle transition.