Hello and thank you for using HCM. I carefully read your question and i totally understated your concern. Let me give you my congratulations for having the courage to succeed in the battle against you breast problem. Acourding to your palpitations my opinion is that you should not be worried. I will try to explain you something. There are different rhythm issues that might give you the sensation of a palpitation. The simplest one are extra-systolic beats. This are electrical impulses generating from parts of the heart different from normal sinus rhythm. They might happen for different reasons from emotional stress to different pathologyes. As it has happen before in a stressed period, probably it is the same thing now. But, just to be sure I recommend you to do an electrocardiogram, echo-cardiograhy and a holter rhythm monitoring. This will give as a better view of your heart structure and rhythm tendency. After that we can evaluate if this palpitations are frequent or just occasionally and nothing to be worried. There is not a relationship between your breast problems and your palpitations in a direct way. Only in rare occasions, the radiotherapy or chemotherapy for breast cancer if you had done so might give heart modifications so you should do an echo-cardiogram just for an evaluation. Hope I was helpful. Wish you good health. Best regards.