Node retrieval in axillary lymph node dissections: recommendations for minimum numbers to be confident about node negative status.

AIMS To determine the minimum number of lymph nodes needed in an axillary lymph node dissection (ALND) specimen to be confident that the axilla is free from metastases. METHODS The Edinburgh Breast Unit selects patients with large and high grade tumours for ALND; 609 consecutive ALNDs performed between October 1999 and December 2002 were reviewed. Full data about the underlying invasive breast cancer were available for 520 patients. Data were collected regarding number of positive nodes and total number of nodes collected, tumour size and grade, and presence of lymphovascular invasion. RESULTS Axillary node metastases were seen in 64% of patients. The mean number of positive nodes found was 3.56, with a mean of 17.9 nodes collected. The highest proportion of patients with lymph node metastases were in the group with 16-20 nodes recovered/specimen (68%); specimens with >20 nodes recovered did not have a higher rate of nodal involvement. There was a significant difference between the proportion of metastasis positive specimens in those with 1-15 nodes recovered (58.5%) and those with 16 or more recovered (69.1%). A linear association test showed a direct correlation between the number of nodes collected and presence of node metastasis (p = 0.0005). CONCLUSIONS Although there is no minimum number of nodes that should be recovered in an ALND specimen, 16 nodes should be regarded as a target to ensure a high level of confidence that the nodes are negative. Node positivity in an ALND specimen appears to obey the law of diminishing returns.