Thyroid desease and breast cancer

I was diagnosed as hypothyroid 6 months before my breast cancer dx. 5 years later I have been dx with papillary thyroid cancer. I had a total thyroidectomy and am now snythroid. Incidentally ultrasound showed nodules on both left and right side, but needle biopsy was negative and my ocologist wanted the thyroid removed, that is when it did prove to be cancer. Both endocrinologis and oncologist said the 2 cancers were related.