Upgrade and Downgrade Rates of Fibroepithelial Lesions in a B3 Lesion Cohort: A 15-Year Analysis from a University Hospital

BACKGROUND: Breast lesions classified as B3 according to UK diagnostic guidelines [1, 2] pose significant management challenges due to their uncertain malignant potential. Within the B3 category, fibroepithelial lesions (FEL) include fibroadenomas (FA), where a phyllodes tumour (PT) cannot be excluded, and benign phyllodes tumours (BPT). OBJECTIVES: To evaluate the upgrade and downgrade rates of B3 classified FA and BPT within a B3 lesion cohort, identify correlations with patient demographics and lesion characteristics, and assess the impact of other variables on diagnostic outcomes. METHODS: Of a total of 332 B3 lesions, a study was conducted on 73 patients with B3-classified FA or BPT diagnosed on core needle biopsy between January 2010 and January 2025. Data on demographics, histological diagnosis, lesion size, imaging findings, procedural data, and subsequent histopathological diagnoses (upgrade or downgrade) were collected. Statistical analyses included multivariate logistic regression. All patients were followed for a median of 8 years. RESULTS: Of 73 FEL cases studied (36 B3-FA, 37 BPT), the B3-FEL downgrade rate was 37% (27/73), and the FEL upgrade rate was 15% (11/73). Downgraded lesions were associated with a significantly lower mean age (32.17 years vs. 40.65 years in non-downgraded lesions, p = 0.027). Multivariate logistic regression identified lower age as the only predictor for downgrade status. The overall long-term recurrence rate was 2.7%. CONCLUSION: Our findings suggest that B3-FELs have high downgrade rates. Younger age is associated with downgrading, while lesion size and ultrasound score are not significant predictors of downgrade. A low long-term recurrence rate of 2.7% was observed. ADVANCES IN KNOWLEDGE: Given the substantially higher downgrade rates in younger patients and the low long-term recurrence rates for B3-FELs, multidisciplinary teams could refine risk stratification and clinical decision-making.