KRT5 and breast cancer: proposed the use of immunohistochemical staining instead of genetic detection to classify molecular subtyping of breast cancer, defined a group of breast cancer cells expressing basal cytokeratins and/or EGFR as BLBC, and pointed out that more than 1% of tumor cells expressed CK5/6 and/or EGFR were the best options for diagnosing the BLBC (12).