Risk Stratification of Breast Fine-Needle Aspiration Biopsy Specimens Performed without Radiologic Guidance by Application of the International Academy of Cytology Yokohama System for Reporting Breast Fine-Needle Aspiration Cytopathology.

BACKGROUND AND OBJECTIVE The International Academy of Cytology (IAC) Yokohama system for reporting breast fine-needle aspiration biopsy (FNAB) cytopathology has been proposed to standardize breast FNAB reporting. The aim of this study was to categorize breast FNAB cases performed by palpation without radiological guidance according to the IAC system, establish the risk of malignancy (ROM) for the categories and assess the system's utility, pitfalls, and implications in low-resource/financial constraint settings. METHODS A retrospective analysis of palpation-guided FNAB of breast lesions performed without radiological guidance between January 2016 and December 2019 was carried out and was correlated with follow-up biopsies wherever available. A total of 1,089 cases were recategorized using the IAC Yokohama system. Histopathology follow-up was available for 400 cases. The data were analysed for ROM, positive predictive value (PPV), and negative predictive value (NPV). RESULTS AND DISCUSSION Out of 1,089 cases, 4.3% (n = 47) cases were categorized as insufficient, 82% (n = 893) as benign, 2.8% (n = 31) as atypical, 2.7% (n = 29) as suspicious of malignancy, and 8.2% (n = 89) as malignant. Some 400 cases had a follow-up biopsy, based on which, the ROM for the categories were 33.3%, 0.4%, 37.5%, 96%, and 100%. The NPV for the benign category was 99.6%. The PPV of the malignant category was 100%, that of combined suspicious of malignancy and malignant categories was 99%, and of combined atypical, suspicious of malignancy, and malignant was 90.6%. CONCLUSION The IAC Yokohama system is useful in standardizing the reporting of cytopathology of breast lesions. FNAB with radiological guidance is ideal but in cases of finance/resource constraints, FNAB by palpation alone is satisfactory if the test result is in the benign, suspicious of malignancy, or malignant categories, which constitute 91.5% of the cases in this study. A repeat ultrasound-guided FNAB and/or core needle biopsy should be recommended for cases in the insufficient/inadequate or atypical categories.