Prognostic Value of Cyclin D1 Overexpression in Invasive Breast Carcinoma

Objective: Breast cancer is the most diagnosed cancer worldwide, accounting for 11.7% of all cancers. Cyclin D1, a regulator of CDK4/6 and cell cycle progression, functions as an oncogene through overexpression, contributing to the pathogenesis of cancers including breast carcinoma. This study aimed to evaluate Cyclin D1 expression and its clinicopathological significance in invasive breast carcinoma within the Turkish population. Methods: H&E-stained and immunohistochemical preparations from partial and total mastectomy specimens of 143 patients, diagnosed between 2007 and 2013, were examined. Cyclin D1 overexpression was evaluated in 1000 cells using an IHC score based on nuclear staining intensity (0-3) and the percentage of positive tumor cells (1-3), classified as weak ('+' or '++') or strong positive ('+++'). Pearson's Chi-Square and Spearman's rho were used to analyze the relationship between Cyclin D1 expression and clinicopathological parameters statistically. Results: The median age of the patients was 58.5 years (Min:28, Max:92). Cyclin D1 status showed no correlation with age, T stage, or lymph node metastasis. However, a moderate positive correlation was observed with ER (r = 0.32, P <.001) and PR (r = 0.31, P <.001) scores. Among molecular subgroups, Cyclin D1 overexpression was most significant in Luminal B group (92.9%, P = .008), while Triple-negative group showed significantly lower overexpression (40%, P = .008). Conclusion: Cyclin D1 overexpression in Luminal B and Luminal A groups, along with its positive correlation with ER, suggests its role in estrogen-sensitive breast cancer pathogenesis. Strong Cyclin D1 overexpression was associated with reduced survival time in HER2-positive cases.