Table 1 The subtypes of breast cancer classified via expression of Ki67 and hormonal status

Luminal A

Estrogen positive (ER +)

Progesterone receptor (PR) ≥ 20%

HER2 negative (HER2-)

Ki67 < 14%

Luminal B (HER2−)

Estrogen positive (ER +)

HER2 negative (HER2-)

Ki67 ≥ 20%

Progesterone receptor (PR) < 20% or progesterone receptor negative (PR-)

Luminal B (HER2+)

Any progesterone receptor (PR) level

Any Ki67 level

HER2 positive (HER2+)

Estrogen positive (ER+)

HER2 positive (HER2+) (non-luminal)

HER2 positive (HER2+)

Estrogen negative (ER-)

Progesterone negative (PR−)

Triple-negative breast cancer (TNBC)

HER2 negative (HER2−)

Estrogen negative (ER−)

Progesterone negative (PR−)