Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 4 1&2 2012 02 01 16 20 EN Nahid Nafissi Cancer Research Center, Shahid Beheshti Medical University, Tehran, Iran Maryam Khayamzadeh Cancer Research Center, Shahid Beheshti Medical University, Tehran, Iran Alireza Sarafzadeh Cancer Research Center, Shahid Beheshti Medical University, Tehran, Iran Mohammad Hashemi Department of Pathology, Shahid Beheshti Medical University, Tehran, Iran Masoud Saghafinia Department of Anesthesiology, Shahid Beheshti Medical University, Tehran, Iran Massoomeh Najafi Department of Surgery, Cancer Institutet, Tehran University of Medical Sciences, Tehran, Iran Asieh Olfatbakhsh Breast Cancer Research Center, ACECR Hasan Rafati Department of Anesthesiology, Shahid Beheshti Medical University, Tehran, Iran Mohammad Esmaeil Akbari Cancer Research Center, Shahid Beheshti Medical University, Tehran, Iran 2012 05 08 2013 02 23 Background: now the vast majority of breast tumors are treated using Breast conservation therapy (BCT) method, including lumpectomy and radiotherapy. This study aimed to evaluate the effects of intraoperative frozen section in patients undergoing breast conservation surgery. Methods: Totally 237 women who included in the category for breast conservative or oncoplastic surgery and post-operative radiotherapy (Early breast cancer Stage I,II and Stage IIIA after neoadjuvant chemotherapy and down staging) were enrolled in  this prospective study from March 2009 to June 2011. Results: In frozen section, totally 88 margins (6.1%) in 60 patients (25%) was positive (1-5 positive margins/ patients) that all of these patients were re-excised. In precise pathologic view the margins in 7 patients (2.9%) was positive that comprised 4% of all margins, furthermore the results showed closed margin in 4 patients. false negative in our study occurred in 0.8% of patients and in 0.1% of margins (sensitivity 100% and specifity 99.2%). Conclusion: we designated intraoperative margin assessment by frozen section as an effective method in decreasing the rate of additional operations for margin control. Additionally, adequate margin width is accessible during same operation. https://bccr.tums.ac.ir/index.php/bccrj/article/view/23 https://bccr.tums.ac.ir/index.php/bccrj/article/download/23/pdf