Association of Poorly Differentiated Clusters with Clinicopathological Features and Tumour Budding Count in Invasive Breast Carcinoma: A Cross-sectional Study

Introduction: Poorly Differentiated Clusters (PDC) and Tumour Budding Count (TBC) have emerged as potential histological markers of tumour aggressiveness. While their prognostic significance is well-documented in colorectal carcinoma, their role in invasive breast carcinoma remains underexplored. Aim: To assess the frequency of PDCs in invasive breast carcinoma and to analyse their association with various clinicopathological factors, tumour budding and molecular profile. Materials and Methods: This cross-sectional study was done from January 2022 to December 2025 at the Department of Pathology, Adichunchanagiri Institute of Medical Sciences, Karnataka, India. Clinicopathological details were noted down and PDC and TBC were assessed and graded on routine Haematoxylin and Eosin (H&E) slides. Further Immunohistochemistry (IHC) was done for Oestrogen Receptor (ER), Progesterone Receptor (PR), Human Epidermal Growth Factor Receptor 2 (HER2), and Ki-67 for molecular classification of tumour. Statistical Package for the Social Sciences (SPSS) software version 25.0 was used to assess association between PDCs and TBC, clinicopathological features and molecular profile of tumour. Chi-square and multivariable logistic regression tests were done and p-value of <0.05 was considered significant. Results: The study included 44 cases of invasive ductal carcinoma breast, no special type. Age of the patients ranged between 34 and 75 years. Majority of cases were of grade 2 (27 cases; 61.36%) and T2 stage (28 cases; 63.64%). PDC showed an association with tumour grade and tumour budding with a p-value of <0.05 and 0.02, respectively. There was no association with lymph node metastasis, lymphovascular invasion and tumour size. Similarly, hormone receptor, HER2 and Ki-67 expression did not show any association (p-value>0.05). On multivariate analysis, only TBC grade 1 showed a statistically significant association with PDC (OR=0.052, 95% CI: 0.003- 0.864, p-value=0.039). Conclusion: PDC evaluation is a simple and cost-effective morphological indicator of tumour aggressiveness on routine H&E section. It may compliment the conventional prognostic factors and aids in improved risk stratification.