TP53 and retinoblastoma: Interestingly, there are some tumors that inactivate the pathway almost exclusively through direct p53 mutation or deletion of its locus, like esophageal squamous carcinoma [10], whereas others are known to abrogate the p53 pathway by other type of mechanisms, such as the amplification of important negative p53 regulators, that have been reported in the majority of liposarcomas, melanomas and retinoblastomas [11].