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Summary: Background: After the ACOSOG Z0011 trial, it became important to evaluate the number of metastatic axillary lymph nodes (LNs) preoperatively. The purpose of this paper is to confirm whether the number of metastases can be accurately diagnosed by preoperative computed tomography (CT), ultrasound sonography (US), and US-guided fine-needle aspiration cytology (FNAC). Methods: We retrospectively analyzed the axillary LNs finding of preoperative CT/US of 470 breast cancer patients. Metastasis was suspected based on the following findings: LNs with a long-axis diameter of ≥10 mm or a short-axis diameter of ≥5 mm on CT, and LNs with the absence of a fatty hilum, focal cortical thickness or a cortical thickness ≥2 mm on US. We also examined the results of FNAC making a rapid bedside diagnosis (bedside-FNAC) of 162 LNs that were suspected to metastatic based on the US findings. Results: On CT, all cases with ≥3 LNs with a long-axis diameter of ≥10 mm and a short-axis diameter of ≥5 mm had metastasis. However, there was no relationship between the number of detected LNs and the number of metastases. On US, 75.7% of LNs with the absence of a fatty hilum and all LNs with cortical thickness ≥6 mm had metastasis. The accuracy of bedside-FNAC for suspicious LNs was 100%. Conclusions: Although we can pick up LNs that are likely to have metastasis on CT/US, it was impossible to accurately predict the number of metastases on CT/US. However, bedside-FNAC of suspicious LNs could accurately predict the number of metastases. Keywords: Bedside fine-needle aspiration cytology, Computed tomography, Lymph node metastasis, Rapid diagnosis, Ultrasound sonography