Suggest Treatment For Stage 2 Breast Cancer

Hi was diagnosed with stage 2 breast cancer. I had a mastectomy and had 4 lymph nodes taken out, one was positive, My Dr who did the mastectomy says I need chemotherapy and radiation, because the lymp nodes was positive either I take all lymph nodes out or have radiation. My oncologist says I only need chemotherapy because I had a mastectomy and the markings where clean. I am confused help!!