Supplementary Material for: CYTOLOGICAL ASSESSMENT OF PAEDIATRIC BREAST LESIONS: A SYSTEMATIC REVIEW

INTRODUCTION Paediatric breast lesions are rare and mostly benign. Despite their benign nature, the presence of these lesions in this population often raises concerns. Fine-needle aspiration biopsy (FNAB) offers a minimally invasive, though its application in paediatric populations remains debated due to interpretative challenges. This systematic review aims to assess the utility, limitations, and diagnostic performance of FNAB in the evaluation of paediatric breast lesions. METHODS A systematic search was performed in Pubmed for articles published from January 2014 to February 2025. Non-humans and non-English language reports were excluded. Based on title and abstract screening, 25 articles were selected, and 13 additional articles were retrieved through reference list, yielding a total of 38 studies for qualitative analysis. Data were manually extracted and synthesized. RESULTS Benign lesions represented the majority of cases, with fibroadenomas being the most frequent (65%–95%), followed by benign phyllodes tumours, hamartomas, tubular adenomas, pseudoangiomatous stromal hyperplasia (PASH), and cystic lesions. Malignant lesions were rare and included metastatic tumours, malignant phyllodes tumours, secretory carcinoma, and primary breast sarcomas. FNAB demonstrated high diagnostic accuracy for benign lesions but showed limitations in distinguishing benign from malignant tumours. ROSE was identified as a valuable adjunct, improving sample adequacy, reducing the rate of inconclusive results and enhancing diagnostic reliability. CONCLUSION FNAB is an effective first-line diagnostic modality for paediatric breast lesions, offering high accuracy for benign conditions. However, limitations exist in discriminating borderline and malignant lesions, warranting correlation with clinical, radiological findings, and, in some cases, core biopsy confirmation. The integration of ROSE enhances FNAB diagnostic yield and may further refine management strategies. A multidisciplinary approach remains essential to ensure optimal, minimally invasive care for paediatric patients.