BACKGROUND: CD133 is a transmembrane glycoprotein and is considered the most common cell surface marker to identify cancer stem cells in hematological and solid tumors, including breast cancer. OBJECTIVES: To evaluate the impact of immunohistochemical expression of CD133 on response rate and survival in metastatic breast cancer, as well as to correlate it with various demographics and clinicopathological characteristics. METHODS: One-hundred metastatic breast cancer patients were prospectively recruited at the Medical Oncology Department at South Egypt Cancer Institute during the period from January 2018 to January 2020. RESULTS: There was a statistically significant correlation between CD133 positive patients with various adverse clinicopathological parameters such as high grade (p= 0.013), higher tumor (p= 0.001), and nodal staging (p= 0.024) during a median follow-up time of 17 months. In addition, Cases with CD133 positive expression had a significantly lower survival time than those with negative expression (3-years OS 37.4% versus 85.5%, p= 0.024). Regarding the response rate, CD133 positive patients had a lower response rate than negative patients (50% versus 54%, p= 0.012). CONCLUSIONS: Positive CD133 is correlated with poor prognosis in metastatic breast cancer patients. 中文翻译： 背景：CD133 是一种跨膜糖蛋白，被认为是识别血液肿瘤和实体肿瘤（包括乳腺癌）中癌症干细胞的最常见的细胞表面标志物。目的：评估 CD133 的免疫组织化学表达对转移性乳腺癌的反应率和生存率的影响，并将其与各种人口统计学和临床​​病理学特征相关联。方法：在 2018 年 1 月至 2020 年 1 月期间，在南埃及癌症研究所内科肿瘤科前瞻性招募了 100 名转移性乳腺癌患者。结果：CD133 阳性患者与各种不良临床病理参数之间存在统计学显着相关性，例如高级别 (p= 0.013)、高级别肿瘤 (p= 0.001) 和淋巴结分期 (p= 0. 024）中位随访时间为 17 个月。此外，CD133 阳性表达病例的生存时间显着低于阴性表达病例（3 年 OS 37.4% 对 85.5%，p=0.024）。关于反应率，CD133 阳性患者的反应率低于阴性患者（50% 对 54%，p = 0.012）。结论：CD133阳性与转移性乳腺癌患者预后不良相关。