triple negative breast cancer
Definition A group of aggressive breast cancers which the Nottingham group defines as breast cancer with a triple negative (non-expression of oestrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2–HER2 receptor profile, and expression of a least one high-molecular weight (basal) cytokeratin–e.g., CK 5/6, CK14, CK17.
Significance Basal-like/triple negative breast cancer accounts for 12 to 17% of all breast cancers. It is more common in younger black and Hispanic women with BRCA1 mutation, and is a common interval cancer. It has a shorter overall survival and disease-free interval in node-negative or node-positive disease, and tends to metastasise to the brain and lung.
While triple-negative and basal-like phenotypes are not synonymous, they overlap (60–90% of triple-negative tumours are basal-like), not are all basal-like cancers are triple negative (but 86-95% are) and share histological features. The therapeutic impact of triple negativity is that these tumours don’t respond to endocrine manipulation nor to anti-HER2 agents, yet despite it all, some subgroups have a good outcome.
Histopathology Syncytial growth pattern, central scarring/necrosis, pushing borders, brisk mitotic activity (>19/10 HPF), grade III atypia with scant cytoplasm, (atypical) medullary features, metaplastic elements (squamous cells, spindle cells), prominent lymphocytic infiltrate.
IHC CK5, CK14, CK17, EGFR, p63, ER, PR, HER2 are typically negative
Synonyms Basal like triple negative breast cancer, basal phenotype tumour, basal tumour of breast, triple negative basal-like breast cancer
References J Clin Oncol. 2008 May 20;26(15):2568-81