Grocott’s methenamine silver stain mediated micronuclei detection: A diagnostic tool for breast lesion classification

Introduction: Micronuclei (MN), markers of chromosomal instability and genetic damage, are emerging as reliable biomarkers in fine needle aspiration cytology (FNAC) of breast lesions. MN scoring aids in distinguishing benign from malignant lesions and may assist in diagnosing borderline cases, improving the accuracy and objectivity of cytological evaluation. This study aims to assess the correlation between MN scoring and epithelial breast lesions and evaluate its utility as a supplementary diagnostic tool in challenging cases. Materials and methods: This prospective study was conducted over one year at Mysore Medical College and Research Institute, involving 208 FNAC smears of breast lesions. Inclusion and exclusion criteria were strictly followed. MN scoring was done using Grocott’s Methenamine Silver stain. Cases were categorized according to the International Academy of Cytology Yokohama System, and malignant cases were graded using Robinson’s criteria. Two independent pathologists scored the slides to ensure good interobserver reliability. Results: Among the 208 cases, 69.7% were benign, predominantly fibroadenomas. MN scores were low in benign lesions (0.3–2.0), increased in atypical and suspicious lesions (3.4 and 5.2), and highest in malignant cases, particularly poorly differentiated tumors (up to 17.4). A positive correlation was observed between MN score and malignancy, with aggressive tumors showing higher genetic instability. Benign lesions were predominantly seen in younger individuals, while the malignant cases showed an upward trend with increasing age. Conclusion: MN scoring correlates strongly with malignancy and provides an objective, reproducible tool in breast cytology, especially valuable in borderline cases such as atypical hyperplasia, enhancing diagnostic confidence in FNAC.