What does grade 3 tumor in right breast mean? like, does that mean a stage, is it fatal, etc...?

Grade 3 = abormal: Grade 3 means the tumor cells are poorly differentiated. Which describes the cells in the tumor. Therefore it shows abnormal breast tissue and is likely cancerous . The staging will describe how far the cancer has spread. Refer to your doctor for more information.

Not the same thing: Tumor grade is on a scale of 1-3, based on the pathologist's opinion of how aggressive a section of tumor appears under the microscope. Tumor stage is on a scale of 0-4, with higher stages correlating with lower survival. I suggest the following information from the national cancer institute website, it is concise and easy to understand -http://www.Cancer.Gov/cancertopics/wyntk/breast.

Maybe: Grade is different from stage. It is a measure of the aggressiveness of the tumor, and helps the oncologist to determine prognosis but stage is actually correlated to outcomes.