RECQL4 and osteosarcoma: Indeed, there are eight currently known syndromes in which osteosarcoma occurs at an increased frequency: Li–Fraumeni syndrome (mutation of TP53 gene); retinoblastoma syndrome (mutation of RB1 gene); Rothmund–Thomson syndrome (mutation of RECQL4 gene); RAPADILINO syndrome (mutation of RECQL4 gene); Werner syndrome (mutation of WRN gene); Bloom anemia (mutation of RECQL3 gene); and Diamond–Blackfan anemia (mutation of S19 gene) [19].