You will have to ask your doctor for the exact pathology report. Precancerous cells are abnormal cells which have an altered multiplcation pattern. What you need to understand is that puts your mother in the high risk category, but for now she does not have a malignant lesion. You need to discuss the type of pre-cancerous cells the pathology reports say - because some are responsive to chemotherapy with tamoxifen and some require radiotherapy. Discuss this in detail with your doctor. Radiotherapy is use of ionizing radiation as part of cancer treatment to control malignant cells or premalignant cells. Radiation Therapy is in itself painless. The side effects vary from patient to patient but usually involve skin lesions or skin changes, swelling etc. This has to be discussed with your physician in detail too. Goodluck.