The expression profiling of the following genes transcripts or proteins has been conducted in FMCs over the last 17 years (Table 1), namely: BCL-2 [76], p53 [77], Cyclin A (apparently not overexpressed in feline mammary tumors [51]), Mst1R [48], ER [50,78], erbB-2 [2,41,63,78,79], COX-2 [80], Pten [75,81], Akt [82], mTOR [83], CXCR4 [84], catenins [85], cadherins [85,86], Twist-1 [49], claudins, CLDNs [87,88], Notch1 [89], PR, CK5/6 [78] or Ki-67 [78,90]. This evidence concerns the gene PGR and breast cancer.