Objective:To investigate the expression status of Thy-1 in malignant cancerous tissues and to evaluate whether Thy-1 could be a potential tumor marker. Methods:Immunohistochemistry method was used to examine Thy-1 expressions in different malignant tumor tissues. We used a monoclonal antibody specific for Thy-1 and the indirect Catalysis Signal Amplification method. With the help of tissue microarray (TMA),we examined expression the status of Thy-1 in 1451 different types of malignant tumor tissues,144 normal tissues and benign lesions. Results:All the malignant tumor cells were grouped as one group (malignant cells group) and normal or benign tumor tissue cells as another group (normal cells group). Among the entire 1451 malignant cases group,positive Thy-1 expression with diffuse and strong staining was observed in 734 (734/1451; 50.59%) cases. In the benign cases only 6 chronic cervicitis cases showed weak staining for Thy-1. All the normal tissue showed negative staining. One-Way ANVOA analysis showed F value between these two groups was 147.229 (P<0.0001). Conclusion:A significantly stronger expression of Thy-1 in malignant tumors was observed. Special overexpression of Thy-1 in malignant tumors suggests that Thy-1 might be a potential novel tumor marker with respect to cancer progression. Chronic cervicitis has some relationship with cervix carcinoma. When it develops into atypical hyperplasia,it will be a precancerous lesion for cervix carcinoma. In this research we found weak staining for Thy-1 in chronic cervicitis lesion,so Thy-1 may play a crucial role in carcinogenesis for cervix carcinoma. The research about the relationship between Thy-1 expressions in cancer cells and in precancerous lesion will provide some clues to understand the mechanism for carcinogenesis process. Objective: To investigate the expression status of Thy-1 in malignant cancerous tissues and to evaluate whether Thy-1 could be a potential tumor marker. Methods: Immunohistochemistry method was used to examine Thy-1 expressions in different malignant tumor tissues. monoclonal antibody specific for Thy-1 and the indirect Catalysis Signal Amplification method. With the help of tissue microarray (TMA), we examined expression the status of Thy-1 in 1451 different types of malignant tumor tissues, 144 normal tissues and benign lesions. Results: All the malignant tumor cells were grouped as one group (malignant cells group) and normal or benign tumor tissue cells as another group (normal cells group). Among the entire 1451 malignant cases group, positive Thy-1 expression with diffuse and strong staining was observed in 734 (734/1451; 50.59%) cases. In the benign cases only 6 chronic cervicitis cases showed weak staining for Thy-1. All the normal tissue showed negative staining. One-Way A NVOA analysis showed F value between these two groups was 147.229 (P <0.0001). Conclusion: A significant stronger expression of Thy-1 in malignant tumors was observed. Special overexpression of Thy-1 in malignant tumors suggests that Thy-1 might be a potential novel tumor marker with respect to cancer progression. Chronic cervicitis has some relationship with cervix carcinoma. When it develops into atypical hyperplasia, it will be a precancerous lesion for cervix carcinoma. In this research we found weak staining for Thy-1 in chronic cervicitis lesion, so Thy-1 may play a crucial role in carcinogenesis for cervix carcinoma. The research about the relationship between Thy-1 expressions in cancer cells and in precancerous lesion will provide some clues to understand the mechanism for carcinogenesis process.