Is it necessary to harvest additional lymph nodes after resection of the most radioactive sentinel lymph node in breast cancer?
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.
Liu
Liang-Chih
LC
Department of Surgery and Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA.
Lang
Julie E
JE
Jenkins
Tyler
T
Lu
Ying
Y
Ewing
Cheryl A
CA
Hwang
Shelley E
SE
Sokol
Shima
S
Alvarado
Michael
M
Esserman
Laura J
LJ
Morita
Eugene
E
Treseler
Patrick
P
Leong
Stanley P
SP
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*
D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals