Ans. is 'a' i.e., Prognosis o Estrogen receptor (ER) positive breast carcinomas are generally slow growing and respond well to hormonal treatment,o Gene expression prolifing, which can measure the relative quantities of mRNA for essentially every gene, has identified five major patterns of gene expression in invasive ductal carcinoma.Luminal Ao This is the largest group (40-55%) which has characteristics of normal luminal cells,o This type is ER positive and HER2/neu negative.o These cancers are generally slow growing and respond to hormonal treatment. Conversely only a small number will respond to standard chemotherapyLuminal Bo These tumors are ER positive, has a higher proliferative rate and overexpresses HER2/neu - Triple- positive cancer.o They compose a major group of ER-positive cancers that are more likely to have lymphnode metastases and may respond to standard chemotherapy.Normal breast lineo These are ER positive, HER2/neu negative and characterized by the similarity of their gene expression pattern to normal tissue.Basal lineo These are ER negative, PR negative, HER2/neu negative - Triple negative.o These are characterized by expression of markers typical of myoepithelial cells (e.g., basal keratins, P- codherins, p63, or laminin), progenitor cells, or putative stem cells (e.g. cytokeratins 5 and 6).o Many carcinoma arising in women with BRAC1 mutations are of this type.o These are aggressive tumors, frequent metastasis to viscera and brain can be seen - have poor prognosis.HER2 positiveo These are ER negative and overexpress HER 2/neu protein.