Accuracy of Breast Fine-Needle Aspiration Biopsy Using the International Academy of Cytology Yokohama System in Clinico-Radiologically Indeterminate Lesions: Initial Findings Demonstrating Value in Lesions of Low Suspicion of Malignancy

Background: Fine-needle aspiration biopsy (FNAB) in breast lesions offers accurate results in differentiating benign and malignant lesions. However, its role is unclear when core-needle biopsy (CNB) is available, the latter providing additional information regarding tumor grade, invasion, and hormone receptor status in malignant lesions. In benign breast lesions, especially in BIRADS category 4a and 4b, FNAB, and CNB provide similar pathological information, whereby FNAB may serve as a more rapid and cost-effective investigation. The study was planned to reevaluate the diagnostic accuracy of FNAB in BIRADS category 4a, 4b, and 4c lesions. Materials and Methods: FNAB and biopsy reports of all patients with breast lesions sent between September 1, 2018, and November 30, 2020, were collected and the International Academy of Cytology (IAC) Yokohama category and BIRADS score were recorded for each case. The rate of malignancy and the accuracy of FNAB in diagnosing malignancy were calculated for each BIRADS 4a, 4b, and 4c subgroup. Results: A total of 249 cases of BIRADS 4 lesions had corresponding cytology and histopathology diagnoses. FNAB showed high diagnostic accuracy in all BIRADS groups. A benign categorization was associated with a very low number of false-negative diagnoses, especially in BIRADS 4a lesions. Conclusion: The study reconfirms the excellent accuracy of breast FNAB using the IAC Yokohama system in diagnosing breast malignancies. Furthermore, BIRADS 4a lesions found to be belonging to the cytological benign category may be excluded from CRB and kept on clinical follow-up.