Tumor subtypes, hormone receptor, HER2, triple negative

Breast cancer is not a single disease. Tumors differ in which receptors they carry, meaning which docking sites sit on the cells. These characteristics determine how a tumor grows and what it responds to.

What is examined above all are the hormone receptors for estrogen and progesterone, the HER2 receptor, and the cell division marker Ki 67. In simplified terms, this leads to four groups:

• Luminal A: hormone receptor positive, HER2 negative, slow growing, favorable outlook.
• Luminal B: hormone receptor positive, growing somewhat more aggressively.
• HER2 positive: many HER2 docking sites, often aggressive in the past, but much more treatable today thanks to targeted therapies.
• Triple negative: neither hormone nor HER2 receptors, about 10 to 20 percent of cases, more aggressive but treatable effectively as well.

Hormone receptor positive tumors respond to anti-hormone therapy, and sometimes chemotherapy can then be skipped. Anti-hormone therapy