O39: THE HISTOPATHOLOGICAL AND MOLECULAR FEATURES OF BREAST CARCINOMA WITH HIGH-GRADE TUMOUR BUDDING

Abstract Background Tumour budding (TB) is an adverse histological feature in many cancers. It is thought to represent epithelial-to-mesenchymal transition, a key step in the metastatic process. The role of TB in breast carcinoma (BC) remains unclear. Aim To investigate the relationship between TB and other histological and molecular features of BC. Method A systematic search was performed to identify studies that compared features of BC based on the presence or absence of high-grade TB. Dichotomous variables were pooled as odds ratios (OR) using the Cochran–Mantel–Haenszel method. Quality assessment of the included studies was performed using the Newcastle-Ottawa scale (NOS). Result Seven studies with a total of 1040 patients (high grade TB n=519, 49.9%; low grade TB n=521, 50.1%) were included. A moderate- to high-risk of bias was noted. The median NOS was 7 (range 6-8). High-grade TB was significantly associated with lymph node involvement (OR 2.28, 95% c.i. 1.74 to 2.98, P<0.001) and lymphovascular invasion (OR 3.08, 95% c.i. 2.13 to 4.47, P<0.001). Regarding molecular subtypes, there was an increased likelihood of high-grade TB in oestrogen- (OR 1.66, 95% c.i. 1.21 to 2.29, P=0.002) and progesterone-receptor positive (OR 1.68, 95% c.i. 1.10 to 2.59, P=0.02) tumours. In contrast triple negative breast cancer had a reduced incidence of high-grade TB (OR 0.46, 95% c.i. 0.30 to 0.72, P=0.0006). Conclusion High-grade TB is enriched in hormone-positive BC and is associated with known adverse prognostic variables. TB may offer new insights into the metastatic processes of luminal BC. Take-home message High-grade TB is enriched in hormone-positive BC and is associated with known adverse prognostic variables. TB may offer new insights into the metastatic processes of luminal BC.