Validation of the International Academy of Cytology Yokohama System for Reporting Breast Fine-Needle Aspiration Cytopathology

Background The International Academy of Cytology (IAC) Yokohama System for the classification of fine-needle aspiration cytology (FNAC) is a diagnostic tool for breast lumps. Cyto-histopathological correlation increases diagnostic precision and is of great relevance. Aim To classify the FNAC of breast lesions according to the IAC Yokohama classification system and to study sensitivity, specificity, and risk of malignancy (ROM) by correlating with histopathological examination. Settings and design A three-year retrospective study of 63 breast FNAC cases with histopathological correlation was performed using the Yokohama System. Materials and methods Taking histopathological diagnosis as the gold standard, diagnostic indices, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), were evaluated. The 63 cases were subsequently recategorized according to the Yokohama System into the following categories: insufficient, benign, atypical, suspicious for malignancy, and malignant. Results The ROM across the Yokohama categories was 0% in Category 1 (insufficient), 1.92% in Category 2 (benign), 33.3% in Category 3 (atypical), and 100% in both Category 4 (suspicious for malignancy) and Category 5 (malignant). When malignant cases were considered positive, the diagnostic performance showed a sensitivity of 87.5%, specificity of 96.4%, PPV of 77.7%, and NPV of 98%. Conclusion The recategorization based on the IAC Yokohama System successfully classifies breast lesions according to their ROM and offers direction for the management strategy of each category. The adoption of the IAC Yokohama System for breast cytopathology reporting, with its standardized terminology, ensures improved diagnostic clarity, consistency, and accuracy, while also facilitating better prediction of the ROM and guiding clinical management and patient outcomes.