Breast Cancer Prognosis: Understanding HER2-Positive Ductal Carcinoma

Question
My sister was diagnosed with breast cancer, she has ductal carcinoma with a lump about 2.54, her erpr is neg and her HER2 is positive. They suspect she has had it for about 5 years. Not sure of the stage yet but she is scheduled for an mastectomy next week.. what is her prognosis or survival rate

Answer
Is her tumor measured in cm or inches? (I suppose you mean 1 inch = 2.54 cm, right?). If indeed it is 1 inch in size it is probably too big for a lumpectomy especially if HER2 positive. So I agree that a mastectomy is the best procedure followed by radiation therapy and chemotherapy. Since it does not have hormonal receptors hormonal treatment is not an option. However to estimate her prognosis I do need to know her stage and the grade of her tumor. Otherwise I can only guess which is not much of a help. A HER2 positive tumor is often more aggressive which makes special chemotherapy important.