MRC1 and endometrial cancer: Practical molecular classification of endometrial cancer according to the MMR status and p53 staining results (MMR 3-tier classification), revealed the best PFS and OS in MMR proficiency with normal p53, followed by MMR deficiency, and finally, MMR proficiency with abnormal p53 (p = 0.005, <0.001) (Figure 4A,B).