For details of Histopathology and Stages of Breast Cancer: watch this series of videos on YouTube https://youtu.be/qm7gd5bYKjQ
Molecular subtype classification of breast cancer  
After the diagnosis of breast cancer using H&E stained biopsy sample, pathologist will classify the the tumor into one of the five molecular subtypes of breast cancer. This is done by  immunohistochemistry (IHC) staining of the biopsy sample using a certain marker protein of interest (see below for details of IHC). Molecular subtyping of breast cancer is important because it largely helps decide the treatment plan for the patient.
The five molecular subtypes of breast cancer are as follows:
  1. Luminal A
  2. Luminal B
  3. HER2
  4. Basal  or Triple Negative Breast Cancer (TNBC)
  5. Normal-like