title: Is it necessary to harvest additional lymph nodes after resection of the most radioactive sentinel lymph node in breast cancer?
abstract: BACKGROUND
  No consensus exists about the number of sentinel lymph nodes (SLNs) that should be removed based on radioactivity counts in breast cancer, although the "10% rule" is often used. We hypothesized that the node with the highest radioactivity would have the strongest probability of being a positive SLN, and we sought to determine the lowest radioactive count of a node harboring cancer.
  
  
  METHODS
  We retrospectively studied 332 breast cancer patients who underwent lymphoscintigraphy by injection of technetium 99m-labeled thiosulfate colloid and sentinel lymphadenectomy (SL) between 1997 and 2006, with intraoperative determination of radioactive counts of nodes by a gamma probe. All SLNs were examined by permanent sections consisting of at least 3 levels of 40- to 100-mum intervals for hematoxylin and eosin evaluation, with or without immunohistochemical staining for cytokeratins.
  
  
  RESULTS
  Seventy-four percent of patients had more than 1 SLN removed (mean 2.8 per patient); 23.5% had SLN metastasis. Of the node-positive patients, the hottest SLN was positive in 85.9% (67 of 78). Five of the 78 patients (6.4%) with positive nodes had counts less than 10% of those of the hottest node. The lowest radioactive count of a positive SLN was 4.2% of that of the hottest node. Lymphatic mapping based on the 10% rule could greatly improve the false-negative rates compared with removing only the hottest SLN (14.1% versus 6.4%).
  
  
  CONCLUSIONS
  Most positive SLNs had the highest radioactivity. Our institutional experience indicates that to obtain an acceptable false-negative rate, nodes should be removed until the 10% rule is met.
authors.affiliation: Department of Surgery and Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Liang-Chih
authors.initials: LC
authors.lastname: Liu
authors.forename: Julie E
authors.initials: JE
authors.lastname: Lang
authors.forename: Tyler
authors.initials: T
authors.lastname: Jenkins
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Ewing
authors.forename: Shelley E
authors.initials: SE
authors.lastname: Hwang
authors.forename: Shima
authors.initials: S
authors.lastname: Sokol
authors.forename: Michael
authors.initials: M
authors.lastname: Alvarado
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Esserman
authors.forename: Eugene
authors.initials: E
authors.lastname: Morita
authors.forename: Patrick
authors.initials: P
authors.lastname: Treseler
authors.forename: Stanley P
authors.initials: SP
authors.lastname: Leong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001365:Axilla; D001943:Breast Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery; D008875:Middle Aged; D015609:Organotechnetium Compounds; D011851:Radioactivity; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*
chemical_list: D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals