Cuevas et al (2019) recently reported that co‐deletion of Pten and Fbxw7 in the mouse endometrium using an alternative BAC‐Sprr2f‐Cre recombinase caused EMT and carcinosarcomas with complete penetrance following somatic acquisition of Trp53 mutations (Cuevas et al, 2019). Here, FBXW7 is linked to carcinosarcoma.