Table 2: The biological subtypes of breast cancer.

SubtypesEstrogen receptor
(ER)
Human epidermal growth factor receptor-2 (HER2)Ki-67
protein
Progesterone
receptor
(PR)
Comment

Luminal A 
Luminal B
Positive 
Positive
Negative 
Positive or Negative
Low 
High
Positive or Negative 
Positive or Negative
In comparing luminal A and B, luminal A is reported to be growing slower than luminal B, which means best prognosis in luminal A cancer; Ki-67 helps in monitoring how fast tumours grow.

Triple-negative (basal-like)NegativeNegative-NegativeIt is defined as basal-like breast cancer and is more common among young women especially with BRCA1 gene mutations.

HER2-enrichedNegativePositive-NegativeThis cancer is growing faster than luminal cancers but with worse prognosis.

Normal-likePositiveNegativeLowPositive or NegativeAlthough ‘normal-like’ is similar to luminal A, its prognosis is worse than luminal A.