TP53 and lymphoma: In addition, two models utilizing TP53 mutations have been developed: a genetically modified pig expressing mutant TP53R167H, which develops lymphomas and osteogenic tumors in homozygous individuals (Sieren et al., 2014), and TP53 knockout pigs that develop spontaneous osteosarcomas in older heterozygous animals and multiple large osteosarcomas in 7 to 8-month-old homozygous pigs (Saalfrank et al., 2016).