title: Highest isotope count does not predict sentinel node positivity in all breast cancer patients.
abstract: BACKGROUND
  Radioisotope mapping is an essential technical component of sentinel lymph node (SLN) biopsy, and most authors define isotope success by an arbitrary threshold SLN-to-background ratio. Few studies have examined the degree to which the relative level of SLN counts correlates with the presence of metastasis. Having removed the SLN with the highest counts, how far should the surgeon persist in removing additional SLN which contain much lower levels of isotope?
  
  
  METHODS
  We performed SLN biopsy, using both radioisotope and blue dye, in 2285 consecutive patients with stage I-II breast cancer. Successful isotope localization was defined as an ex vivo SLN-to-axillary background count ratio of at least 4:1, and enhanced pathologic analysis (serial sections and immunohistochemistry) was used throughout.
  
  
  RESULTS
  Among the 1566 patients with more than one SLN site identified, the SLN contained metastasis in 463 (30%). In 369 (80%) of these SLN-positive cases, the SLN with the highest count contained tumor, but in 94 (20%) it was benign. Among these 94: (1) the counts of the hottest benign SLN exceeded those of the histologically positive SLN by a ratio of at least 10:1 in 31% (29 of 94) of cases, (2) the counts of the positive SLN were < 4:1 those of the axillary background in 16% (15 of 94) of cases, and (3) blue dye failed to identify 27% of positive SLN. No optimum ratio of SLN-to-SLN or SLN-to-background counts identified the positive SLN in all cases.
  
  
  CONCLUSIONS
  Although the SLN with the highest counts is positive in 80% of breast cancer patients with multiple SLN, neither a relatively high isotope count nor the presence of blue dye consistently predict SLN positivity in all breast cancer patients. For maximum accuracy, SLN biopsy requires (1) the removal of all nodes containing isotope regardless of the relative magnitude of counts, (2) the concurrent use of blue dye to salvage those procedures in which isotope fails, and (3) the removal of all clinically suspicious non-SLN.
authors.affiliation: The Breast Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Martin
authors.forename: J
authors.initials: J
authors.lastname: Fey
authors.forename: H
authors.initials: H
authors.lastname: Yeung
authors.forename: P I
authors.initials: PI
authors.lastname: Borgen
authors.forename: H S
authors.initials: HS
authors.lastname: Cody
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012394:Rosaniline Dyes; D021701:Sentinel Lymph Node Biopsy / Q000379:methods; D013671:Technetium Tc 99m Sulfur Colloid
chemical_list: D019275:Radiopharmaceuticals; D012394:Rosaniline Dyes; C025484:iso-sulfan blue; D013671:Technetium Tc 99m Sulfur Colloid