ERBB2 and breast cancer: “ER,” “PR,” and “HER2” are cell receptors canonically used for breast cancer subtyping, “T” represents the size of the original tumor and whether it has invaded nearby tissue, “N” describes the nearby lymph nodes involved, “TNM stage” is an international standard for classifying the extent of spread of cancer based on “T,” “N,” and “M” (“M” describes distant metastasis).