Internal mammary lymph node irradiation (IMLNI) could reduce local recurrence and distant recurrence and improve survival.The NCCN Guidelines have updated the recommends in IMLNI.However, the relative toxicities of IMLNI to the heart and lungs should be carefully considered by clinicians, so individualized indications for IMLNI are needed.Internal mammary sentinel lymph node biopsy (IM-SLNB) could be an accurate technique to guide IMLNI with minimally invasive staging, and provide more survival benefits to patients.This article reviews the benefits of IMLNI, controls of the side effect, and discussion of IMLNI guided by IM-SLNB.