AB034. SOH25_AB_197. Upstage rates and risk factor analysis of pure intraductal papilloma lesions in the breast

Background: B3 intraductal papilloma (IDP) breast lesions are frequently excised due to the possible presence of cancer and carcinoma in situ. However, this approach can expose patients to unnecessary surgical risks and complications, while also utilising valuable theatre time. Recent studies have demonstrated that active surveillance may be suitable for lower risk IDPs. The aim of this study was to analyse cases of pure IDP breast lesions in St. Vincent’s University Hospital to identify upstaging rates and risk factors.

Methods: The study retrospectively analysed core needle biopsies performed between 2013–2023 with a histological diagnosis of pure IDP. Upstaging rates from pure IDP to carcinoma-in situ or cancer were calculated and stratified according to the presence of atypical cells. Logistic regression was utilised to identify characteristics associated with upstaging. Fisher’s exact test was used to analyse categorical variables.

Results: There were 260 patients without atypia and 27 patients with atypia in the IDP. Combined upstaging rates were 5.77% (without atypia) and 11.11% (with atypia). IDP size was identified as significant in predicting upstaging (P=0.01). Papilloma size of 12 mm or greater was associated with increased risk of malignancy [P=0.032, odds ratio (OR) 3.14, 95% confidence interval (CI): 1.104–8.930].

Conclusions: Low upstage rates suggest active surveillance is suitable for IDPs after consideration of high-risk factors such as size. A small upstaged group sample size is a limitation in this study. Further research should focus on creating larger, balanced datasets, to accurately model high-risk features of IDPs and assess their performance in predicting long term upstaging risk.

Keywords: Atypia; papilloma; risk; size; upstaging