TP53 and keratoacanthoma: To avoid keratoacanthomas and to temporally and spatially restrict tumor formation to develop a preclinical model to study FUS-CHOP-driven sarcomagenesis in vivo, we generated the Rosa26 FUS-CHOP; p53 (FCP) model, which delivers a plasmid (pSECC-sgp53) that contains Cre to activate expression of FUS-CHOP, and Cas9 and a p53 single guide RNA (sgRNA), sgp53, to create insertions/deletions (indels) in p53 (Figure 3) [30].