TP53 and sarcoma: Although mice heterozygous for the p53+/515A mutant allele develop tumors (i.e., lymphomas or sarcomas) with similar latency to p53+/− mice [27], we hypothesized that in mice that had also undergone Cre-mediated conditional inactivation of Brca1, ovarian carcinoma development might either out-pace or occur coincidentally with tumors at other sites.