Demystifying breast cancer
Four discrete molecular subtypes of BC are recognized on the basis of an ER-PR test and HER2 status, which informs a specific treatment regimen and is predictive of disease recurrence and mortality rate.
Abstract
Pathology Initial pathology reports for BC will have both pathologic and immunohistochemical information, including the following2: • Cell type: Ductal carcinoma is the most common cell type, followed by lobular carcinoma; however, other rarer cell types are possible. • Grade: This measures disease aggressivity, ranging from well-differentiated (grade 1) to poorly differentiated (grade 3). • Estrogen receptor (ER)–progesterone receptor (PR) test status: This test indicates sensitivity to estrogen and progesterone and is predictive of response to endocrine therapy. • Human epidermal growth factor receptor 2 (HER2) (also known as erb-b2 receptor tyrosine kinase 2 [ERBB2]) gene status: This measures the overamplification of HER2. Overexpression of this transmembrane receptor in BC causes uncontrolled cell growth and replication.1 Four discrete molecular subtypes of BC are recognized on the basis of an ER-PR test and HER2 status: luminal A (ER-positive, PR-positive, HER2-negative); luminal B (ER-positive, PR-positive or PR-negative, HER2-positive or HER2-negative); HER2 (ER-negative or PR-negative, HER2-positive); and triple-negative (ER-negative or PR-negative, HER2-negative).3,4 Each subtype informs a specific treatment regimen and is predictive of disease recurrence and mortality rate.5