Abstract: Objective To investigate the value of cytokeratin(CK)and Vimentin in diagnosing primary pulmonary sarcomatoid carcinoma(PSC)and their correlations with clinical prognosis. Methods A total of 139 patients with suspected PSC were selected as study group, and samples of normal lung tissues of 30 healthy people were collected as control group. Immunohistochemistry was used to detect the expressions of CK and Vimentin in tumor tissues and normal lung tissues. The postoperative pathological diagnosis was considered as gold standard for PSC, and the sensitivity, specificity, the area under curve(AUC)and 95% confidence interval(95%CI)of CK and Vimentin in the diagnosis of PSC were calculated by the receiver operating curve(ROC). All the patients with PSC were followed up for 3 years, and the 3-year survival rate was observed. Multivariate analysis was carried out by using Cox proportional risk regression model. Results Of the 139 patients with suspected PSC, 132 cases were confirmed by pathological results, and 7 cases were diagnosed as small cell lung cancer. The positive expression rates of CK and Vimentin in the study group were 95.68% and 97.84% respectively, but there was no case with positive expressions of CK and Vimentin in the control group, and there were significant differences in positive expression rates of CK and Vimentin between two groups(P<0.05). ROC showed that the sensitivity, specificity, AUC and 95%CI of CK for diagnosis of PSC were 0.985, 0.904, 0.952 and 0.899 to 1.000 respectively, while those of Vimentin - for diagnosis of PSC were 1.000, 0.919, 0.959 and 0.908 to 1.000 respectively. The 1-year and 3-year survival rates of 132 patients with PSC were 81.06% and 56.06% respectively. Cox risk model analysis showed that tumor size, distant metastasis, positive expressions of CK and Vimentin were risk factors affecting the 3-year survival rate of patients(P<0.05). Conclusion CK and Vimentin have certain clinical values in the diagnosis and prognosis evaluation of PSC.