International Academy of Cytology Yokohama System for Reporting Breast Fine-Needle Aspiration Biopsy Cytopathology: A Review of Predictive Values and Risks of Malignancy

Objective: We aimed to assess the risk of malignancy (ROM) and predictive values in prior breast cytology studies as a basis for the new International Academy of Cytology (IAC) Yokohama system for reporting breast fine-needle aspiration biopsy (FNAB) cytology, which classifies cytologic diagnoses into 5 categories: (1) insufficient material, (2) benign, (3) atypical, (4) suspicious of malignancy, and (5) malignant. Study Design: Publications between January 1, 1997, and December 31, 2017, that studied the performance characteristics of FNAB from palpable and nonpalpable breast masses were identified through the PubMed database. Data for number of total cases and cases within each diagnostic category, if available, were collected. Performance characteristics, including absolute sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and ROM for each category were recorded or, when possible, calculated. Results: The literature review resulted in a case cohort of 33,341 breast FNABs, drawn from 27 studies. Pooling these cases together, the ROM for insufficient material, benign, atypical, suspicious, and malignant were 30.3, 4.7, 51.5, 85.4, and 98.7%, respectively. The complete sensitivity and specificity were 96.3 and 98.8%, correspondingly. The PPV and NPV were 98.7 and 95.3%, correspondingly. The false-negative and false-positive rates were 3.7 and 1.0%, respectively. Conclusions: This meta-analysis demonstrates that the diagnostic categories of the new IAC Yokohama System each carry an implied ROM, which increases from the benign to malignant categories. This study also shows the high sensitivity and specificity of FNAB for breast lesions.