Introduction: Breast carcinoma (BC) is the commonest cancer in Sri Lanka. It is a heterogenous disease with wide variation in prognosis. Prognostic factors play key roles in selecting the most appropriate treatment. Tumour budding (TB) has emerged as a new prognostic marker for some cancers. TB is defined as isolated single cancer cells or clusters of up to four cancer cells located at the invasive tumour front. TB still has no recommended grading system for BC and yet to find its place in BC management guidelines. Hence, this study was aimed to determine the prognostic value of TB in invasive BC in a cohort of patients.

Method: All patients fulfilling the inclusion criteria of the current study were selected from the BC data base of the Department of Pathology, Faculty of Medicine, University of Ruhuna which included all BC patients who sought the services of the immunohistochemistry laboratory from 2006-2015. Tumour buds in hotspots were counted in histology slides and graded according to the recommended grading for TB in colorectal cancers. Kaplan Meier model and log rank test were used for recurrence free and BC specific survival (RFS, BCSS) analysis.

Results: A total of 231 BC patients were studied. Majority were 36-60 years of age (63.9%) and had lymph node metastasis (61.3%). Most tumours were 2-5 cm (77.2%) in size and Nottingham grade 2 (n=227, 50.6%) without lympho-vascular invasion (n=221, 64.3%). Most were hormone receptor negative (estrogen receptor-57.1%, progesterone receptor-56.7%) and HER2 negative (n=230, 80.9%). Low-grade (0-4TBs), intermediate-grade (5- 9TBs) and high-grade TB(≥10TB) was present in 40.3%, 22.5% and 37.2% BCs respectively. Five-year RFS and BCSS of the study cohort were 77.2% and 86.5% respectively. TB grade had an independent effect on RFS and BCSS (p=0.027) imparting a poor survival when the tumour had high grade TB.

Conclusion: TB has a significant negative effect on RFS and BCSS of invasive BC patients independent of established prognostic factors.