Subtyping of triple-negative breast cancer.

IM These are not considered official categories at this point, but in an article published in the Journal of Clinical Investigation in 2011, a team led by Lehmann and Pietenpol described 6 subtypes: basal-like 1, basal-like 2, immunomodulatory, mesenchymal, mesenchymal stem-like, and luminal androgen receptor (LAR). “Unclassified” is considered to be a seventh subtype. Between 10% and 20% of breast cancers are triplenegative, meaning that they do not express estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2 (HER2) genes. Of these, approximately 40% fall into the basal-like 1 or 2 subtype, and approximately 10% fall into the LAR subtype.