My mom has recently been diagnosed with IDC grade 2, invasive tumour in dermis and all first 8 lymph nodes tumour free with TNM: pT1, pN0, pMx. The tumour size is 0.8x0.7cm. The epidermis of skin is tumour free however tumour is identified in lower dermis. Tumour cells express E-Cadherins and are ER/PR positive and HER +2. The doctor has done Mastectomy and now advicing us that she would have radiation therapy for 4 weeks, may or may not with chemothrapy or 5 years medicine. I don't have any idea what to do as i can't understand why radiation is needed after mastectomy. If radiation is necesaary, what type is right for this kind of cancer (external or internal) and what dose is recommended? Further, why chemotherapy is needed in this case? Early suggestions would help.