Background:

CD133 is a transmembrane protein, identified as a cancer stem cell marker, and its prognostic significance in various malignancies, including breast cancer, has been studied. This study aims to investigate the prognostic significance of CD133 expression in breast cancer and its correlation with the Nottingham Prognostic Index (NPI). Methods This retrospective cohort study examined specimens from female patients diagnosed with Invasive Breast Cancer (IBC). CD133 expression was evaluated using the H-score based on staining intensity. Patient data such as age, tumor dimensions, Nottingham Prognostic Index, and other clinicopathological parameters were collected. Comparative univariate analysis and correlation analysis were performed. Results Our study included 60 patients, with significant differences in CD133 H-score values were observed among lymphovascular invasion (LVI) patients (p < 0.001), patients with metastasis (p < 0.001), and patients with NPI (p = 0.005). There was a significant positive correlation between CD133 H-score and NPI (r: 0.31; p0.014) and also between NPI and tumor size (r: 0.66; p0.001). Conclusion Our findings suggest that CD133 may serve as a prognostic marker in breast cancer, with higher expression levels linked to more aggressive disease characteristics and a poorer prognosis as indicated by NPI.