Dear millerpuryear, Nuclear grade refers to the growth rate of the cell and how odd-looking the nucleus of the cell is. Pathologists usually grade on a scale of 1-3 or 1-4, with a higher number being worse. When talking about grade alone they are looking at different features of a cell (such as size, shape, activity of the cell) that are combined together to give an overall score that is then translated into a grade. There is some degree of subjectivity to the interpretation of the cells by the pathologist. However after the lumpectomy there was more tissue which could explain the different nuclear grade of cancer.
Also noted from the above is the intraductal carcinoma means there is an invasive component, this finding will be what is concentrated on in terms of treatment etc. At this point because there not being clear margins after the lumpectomy further surgery would be recommended. If lymphnodes have not been removed, a lymph node dissection which removes lymph nodes for examination in the fat pad under the arm.
Based on the above information, I don't know why a mastectomy would be recommended for the right breast.
At this point more information is needed, such as lymph node status, before the stage of your mother's cancer is known. This information is used to determine recommendations for further treatment, treatment is discussed in terms of risks (side effects) and benefits (decrease in recurrence rates and survival rates).
Actually, what you stated in the pathology report does not indicate an invasive component. I think the recommendation for mastectomy is because the tumor cells are extensive within the breast, which has a high recurrance if treated by lumpectomy/radiation, especially with the comedo type. However, cure rate is still extremely high. Because microinvasion is possible even when not seen so far, it's not unusual to check a lymph node at the time. As to the opposite breast; it's not carved in stone: but when there's that extensive disease on one side, the chance of developing it on the other is fairly high. So the choice is to eliminate that risk by "prophylactic" mastectomy, versus watching carefully. It's an area for personal choice: some women would sleep easier not worrying about it. Others would be happier not doing anything unless something showed up; hopefully if it did, it would be non-invasive as it is on this side.