Sentinel lymph node (SLN) detection by lymphoscintigraphy (LS) and using intraoperative gamma probe is the mostly important prognostic factor in patients with breast cancer. Sentinel lymph node biopsy (SLNB) is a procedure that collaborated by nuclear medicine, surgical oncology and pathology medical disciplines, scientifically proven and established into routine. The aim of this guideline is to inform current knowledge about standart LS and SLN procedure and indications in breast cancer and to lead for nuclear medicine practitioners. The recommendations in this guide has been prepared by ‘Turkish Society of Nuclear Medine Oncology Task Group’ members.