Cyclin D1 Overexpression in Breast Carcinoma and Its Correlation with Standard Clinicopathological Parameters

Background: Breast cancer remains the most frequently diagnosed malignancy among women worldwide, with a significant disease burden in India where incidence is rising at younger ages. Conventional prognostic and predictive markers, including ER, PR, and HER2, play a central role in guiding management, yet outcomes remain variable. Cyclin D1, a cell cycle regulatory protein encoded by CCND1, is increasingly recognized as a potential biomarker in breast cancer due to its role in cell cycle control and interaction with hormone receptor pathways. Evaluating Cyclin D1 expression and its association with established prognostic markers may provide valuable insights into disease behavior and therapeutic response. Materials and Methods: This study was carried out on 40 histologically confirmed cases of breast carcinoma. Expression of Cyclin D1, ER, PR, and HER2/neu was assessed using standard IHC protocols and scored according to ASCO/CAP guidelines. Statistical analysis was performed, with p < 0.05 considered significant. Results: Cyclin D1 expression was detected in 23 (57.5%) out of 40 cases. Cyclin D1 expression showed a significant positive correlation with ER (p < 0.001) and PR (p < 0.001) status, but not with HER2/neu. Significant association was also observed between Cyclin D1 and molecular subtypes (p < 0.001), with positivity in all Luminal A and Luminal B cases, and negative correlation with TNBC. Conclusion: Cyclin D1 expression was significantly associated with ER, PR, and Luminal A/B subtypes, but not with HER2, age, or nodal status, and showed negative correlation with TNBC. These findings suggest Cyclin D1 as a potential biomarker in hormone receptor–positive breast cancers, meriting validation in larger studies.