- Chosen by Voters The first answer confuses grade with stage – grade refers to how the cancer looks under the microscope, stage refers to the size of the tumour and the extent of the spread..There are three breast cancer gradesGrade I – cancer cells resemble normal cells and are not growing rapidly Grade 2 – cancer cells have features between grades I and 3 Grade 3 – cancer cells look more abnormal and may grow or spread more aggressively So yes, grade 3 is the most serious. But this doesn't mean it's untreatable. There are no guarantees, but I had grade 3 breast cancer and am fit and well with no evidence of cancer almost five years after diagnosis, having had surgery, chemotherapy and radiotherapy.Your friend – and you – may be interested in these sites; they have loads of information (especially the first one) and forums where you can talk to people who are or have been in the same situation, and read others' experiences of breast cancer and treatment. I don't know what I would have done without online support forums in those dark days after diagnosis or during treatmenthttp://www.breastcancer.orghttp://www.breastcancercare.org.uk 3 years ago 100% 1 Vote 1 person rated this as good