To compare the value of cytokeratin fragment 21-1 (CYFRA 21-1) concentration in the fine-needle biopsy aspirates (fine needle aspirate [FNA] CYFRA 21-1) with cytopathology of fine-needle aspiration biopsy (FNA cytology) and to assess whether CYFRA 21-1 concentrations from ultrasound-guided fine-needle aspiration biopsy (US-FNAB) specimens (FNA CYFRA 21-1) is not inferior to FNA cytology in the diagnosis of axillary lymph node (ALN) metastasis of breast cancer patients. This study received institutional review board approval, and written informed consent was obtained from all patients. US-FNAB was performed in 373 ALNs from 358 patients with invasive breast cancer. Concentrations of CYFRA 21-1 were measured from washouts of the syringe used during US-FNAB (FNA CYFRA 21-1), and ALN metastasis was determined using a cutoff value of 1.93ng/mL. FNA cytology, intraoperative sentinel lymph node biopsy, and surgical pathology results were reviewed and analyzed. The noninferiority margin for the difference in accuracies between FNA cytology and FNA CYFRA 21-1 was set as 5%. Among 373 ALNs, 136 (36.5%) were benign, and 237 (63.5%) were metastatic. The mean FNA CYFRA 21-1 was significantly higher in metastatic ALNs compared to that in benign ALNs (P=0.001). For the diagnosis of ALN metastasis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FNA CYFRA 21-1 (cutoff value 1.93ng/mL) were not significantly different from those of FNA cytology (P>0.05). FNA CYFRA 21-1 reached statistical noninferiority to FNA cytology in terms of diagnostic accuracy for ALN metastasis. Of the 20 ALNs (8 metastasis, 12 benign) that showed insufficient results on FNA cytology, FNA CYFRA 21-1 accurately diagnosed 15 ALNs (4 metastasis, 11 benign). The diagnostic performance of FNA CYFRA 21-1 is comparable with that of FNA cytology for breast cancer ALN metastasis. Our results indicate that FNA CYFRA 21-1, using an US-FNAB specimen, can be a useful method equal to FNA cytology in terms of diagnostic accuracy.
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