Dear orneville: Bilateral mastectomy is a reasonable option if both problems are invasive, although it is not necessary. The choice to do a mastectomy on the breast with lobular cancer may make more sense, since lobular cancer often has projectiles making a successful lumpectomy more difficult. You could do a lumpectomy in the ductal breast - if you went this route, you would need radiation therapy. The final pathology, along with lymph node dissections ,if these are invasive, will determine the stage. The stage, in turn, will help determine the followup treatment. If in fact, these are both stage 1. They are different primary cancers, neither chemotherapy nor radiation therapy may be necessary. In general terms, consider this, you have 2 primary cancers, they can be treated as individual problems. Overall, treatment would be designed based on the one that is worse. In any case, you should see an expert breast oncologist who can help advise you. Hormone therapy will likely be recommended.