Axillary lymph node metastasis: Fine-needle aspiration biopsy sensitivity as a function of node size, percent replacement of lymph node by tumor and tumor deposit size.

BACKGROUND: Fine-needle aspiration (FNA) is commonly used to investigate lymphadenopathy of suspected metastatic origin. While diagnostic accuracy of FNA for lymph node disease is well described, the relationship between node size, percent tumor replacement, and size of metastatic deposit with diagnostic accuracy is less well documented.

METHODS: All axillary lymph nodes undergoing ultrasound-guided FNA for suspected breast metastases were correlated with subsequent surgical excision specimens. FNAs were judged as positive or negative for malignancy and the percent of false negative FNAs was correlated with node size, percent tumor replacement and size of metastatic deposit RESULTS: Sensitivities were calculated for nodes greater than 15 mm (92%), nodes 11 to 14.9 mm (83%), nodes 7 to 10.9 mm (61%), and for nodes less than 7 mm (60%). Sensitivity increases with increasing node size (P = .001). Percent tumor replacement correlated with sensitivity: 90% or greater replacement (85%) 60% to 89.9% replacement (75%), 40% to 59.9% replacement (75%) and less than 39.9% replacement (64%)(P < .001). Metastases size correlated with sensitivity: metastases greater than 10 mm (94%), 6 to 9.9 mm (70%), 4 to 5.9 mm (54%), and less than 4 mm (72%).

CONCLUSIONS: Percentage of false negative FNAs associate with investigation of metastatic disease correlates with node size, size of metastatic deposit and percentage of nodes replaced by tumor. Lymph nodes smaller than 7 mm, deposit diameter less than 6 mm and percentage replacement of less than 40% have the highest percentage of false negative results.