ESR1 and CDH1-related diffuse gastric and lobular breast cancer syndrome: In clinical practice, a few characteristics, such as estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki67 expression, are currently used to distinguish LBC-A (ER+ and/or PR+, HER2-, low Ki67) from LBC-B (ER+ and/or PR+, HER2- or HER2+, high Ki67)4.