title: False negative rate for intraoperative sentinel lymph node frozen section in patients with breast cancer: a retrospective analysis of patients in a single Asian institution.
abstract: OBJECTIVE
  Intraoperative frozen section of the sentinel lymph node (SLN) in clinically node negative breast cancer patients detects metastatic disease and enables axillary lymph node dissection to be performed in the same operative setting. Internationally, the false negative rate (FNR) for SLN biopsy ranges from 5.5% to 43%. The size of SLN metastasis has been identified as a key factor affecting FNR. We review our institutional experience on the accuracy of intraoperative SLN biopsy.
  
  
  METHODS
  Data were collected retrospectively from patients undergoing SLN biopsy performed at Singapore General Hospital. The SLN was identified using blue dye, radioisotope or both. Frozen section was performed intraoperatively. When SLN was positive for metastasis on frozen section, completion axillary clearance was performed. False negative cases were defined as patients in whom a negative frozen section result was obtained, whose final permanent paraffin section was positive. We determined the FNR of SLN frozen section and evaluated the factors associated with it.
  
  
  RESULTS
  A total of 2202 SLN biopsies were performed between January 2005 and June 2012. There were 89 false negative cases, of which there were 23 (25.8%) cases of isolated tumour cells (ITCs), 49 (55.1%) cases of micrometastasis, and 17 (19.1%) cases of macrometastasis. The overall FNR was 13.5%. FNR was 79.3% in ITCs, 59.8% in micrometastasis, and 3.1% in macrometastatic disease. Non-ductal histological subtype, absence of lymphovascular invasion and the size of SLN metastasis were identified as significant independent factors associated with a higher FNR.
  
  
  CONCLUSIONS
  FNRin our institution is acceptable when compared to other large centres. Failure to detect metastasis in frozen section in more than half of our patients was due to ITCs and micrometastasis.
authors: Department of General Surgery, Singapore General Hospital, Singapore.
authors: Jolene
authors: J
authors: Wong
authors: Department of Surgical Oncology, National Cancer Centre, Singapore.
authors: Wei Sean
authors: WS
authors: Yong
authors: Department of Pathology, Singapore General Hospital, Singapore.
authors: Aye Aye
authors: AA
authors: Thike
authors: Department of Pathology, Singapore General Hospital, Singapore.
authors: Jabed
authors: J
authors: Iqbal
authors: Department of Pathology, Singapore General Hospital, Singapore.
authors: Ahmed Syed
authors: AS
authors: Salahuddin
authors: Department of Surgical Oncology, National Cancer Centre, Singapore.
authors: Gay Hui
authors: GH
authors: Ho
authors: Department of Surgical Oncology, National Cancer Centre, Singapore.
authors: Preetha
authors: P
authors: Madhukumar
authors: Department of Surgical Oncology, National Cancer Centre, Singapore.
authors: Benita Kiat Tee
authors: BK
authors: Tan
authors: Department of Surgical Oncology, National Cancer Centre, Singapore.
authors: Kong Wee
authors: KW
authors: Ong
authors: Department of Pathology, Singapore General Hospital, Singapore.
authors: Puay Hoon
authors: PH
authors: Tan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001943:Breast Neoplasms / Q000473:pathology* / Q000601:surgery; D005188:False Negative Reactions; D005260:Female; D005629:Frozen Sections; D006769:Hospitals, General; D006801:Humans; D007430:Intraoperative Care; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008875:Middle Aged; D061206:Neoplasm Micrometastasis; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D021701:Sentinel Lymph Node Biopsy; D012846:Singapore; D055815:Young Adult
keywords: BREAST CANCER; LYMPH NODE PATHOLOGY; SURGICAL PATHOLOGY