Dear booklady: It could well be a reaction to the radiation therapy. However, you should have your doctor check it out. It is always better to make sure all is okay. That way you won't need to worry unnecessarily
the changes you describe can occur from and linger long after radiation, especially in a large breast. Not being able to see or examine, there's no way for anyone online to be sure. But most likely it's radiation change. Any woman who's been through cancer treatment needs close and careful followup.