Furthermore, we observed that only four mice heterozygous for the Pten floxed allele, among 21 R26-Ptenfx/+ mice analyzed, developed a variety of malignancies (up to 60 weeks).The incidence (19.0%, 4 of 21), latency (42 to 58 weeks) and spectrum (lung, breast and liver cancers) of the malignant tumors in our R26-Ptenfx/+ mice is quite different from that of a previous reported Pten+/− mouse model [9]. This evidence concerns the gene PTEN and cancer.