High TFF1 expression was significantly associated with a low grade of malignancy in non-invasive (pTa) urothelial carcinomas of the urinary bladder (p = 0.0072), low grade of malignancy (p < 0.0001), estrogen (ER) and progesterone receptor (PR) expression and non-triple negativity (p < 0.0001 each) in invasive breast cancer of no special type, as well as with right-sided tumor location (p = 0.0021), MMR deficiency (p = 0.0292), RAS mutations (p < 0.0001), and BRAF mutation (p = 0.0331) in colorectal adenocarcinomas. The gene discussed is PGR; the disease is mismatch repair cancer syndrome 1.