目的：探索临床上乳腺癌化疗失败是否与多药耐受表型Ｐ糖蛋白（Ｐｇｐ）有关。方法：使用抗Ｐｇｐ的单克隆抗体的免疫组织化学方法（ＳＰ方法）和微波加热抗原修复技术检测５６例乳腺癌患者组织切片Ｐｇｐ表达状况。结果：（１）术前未接受任何化学治疗的乳腺癌Ｐｇｐ表达的阳性率为７６８％（４３／５６），并且Ｐｇｐ表达程度与提示乳腺癌疾病进展和预后的各项临床病理参数，如年龄、原发灶大小、淋巴结转移数、ＴＮＭ分期、病理学类型和组织学分级无显著相关性（Ｐ＞００５）；（２）Ｐｇｐ阴性组的总体生存率及各时点生存率明显高于阳性组（Ｐ＜００１），经ＣＯＸ多元回归分析模型调整各因素的作用后，Ｐｇｐ对生存率的影响仍然是显著的（Ｐ＜０２，检验水平α＝０．２）。结论：（１）Ｐｇｐ存在于化疗药物作用以前的原发性乳腺癌中，药物耐受是先天性的。（２）Ｐｇｐ在预测药物耐受，化疗反应和预后生存方面有重要作用 Objective: To explore whether clinical breast cancer chemotherapy failure is related to multidrug resistance phenotype P glycoprotein (P  gp). Methods: The expression of Pgp in tissue samples of 56 patients with breast cancer was detected by immunohistochemical method (SP method) with monoclonal antibody against Pgp and microwave heating antigen retrieval. Results: (1) The positive rate of P  gp expression in breast cancer without any chemotherapy before surgery was 76.8% (43/56), and the degree of expression of P  gp was correlated with the progress of breast cancer and its prognosis. Clinical pathological parameters such as age, primary tumor size, lymph node metastasis, TNM stage, pathological type, and histological grade were not significantly related (P>005); (2) Overall survival rate of Pgp negative group The survival rate at each time point was significantly higher than that of the positive group (P<001). After adjusting the effects of various factors by multiple regression model of COX, the impact of Pgp on survival rate was still significant (P<02). , test level α = 0.2). Conclusions: (1) Pgp is present in primary breast cancer before chemotherapy. Drug tolerance is congenital. (2) Pgp plays an important role in predicting drug tolerance, chemotherapy response and prognosis survival