AIM:To investigate the expression of thymidylate synthase(TS)and glutathione-s-transferaseπ(GST-π) in esophageal squamous cell carcinoma and their association with the clinicopathologic characteristics. METHODS:Immunohistochemical methods were used to detect the expression of TS and GST-πin surgically resected formalin-fixed,paraffin-embedded esophageal squamous cell carcinoma(ESCC)tissue sections from 102 patients(median age,58 years)and in 28 normal esophageal mucosa(NEM)samples.The relationship between TS and GST-πexpression and clinicopathologic factors was examined. RESULTS:The expression of TS and GST-πwas not statistically significantly associated with age of the patients,tumor size,lymph node metastasis,depth of invasion or tumor stage.TS staining was positive in 17.86%of normal esophageal mucosa and in 42.16% of ESCC samples(P<0.05).The expression level of TSwas not only significantly lower in well-differentiated (21.88%)than in poorly-differentiated carcinomas (51.43%,P<0.05),but was also significantly higher in samples from male patients(46.51%)than from female patients(18.75%,P<0.05).GST-πwas positively stained in 78.57%of normal esophageal mucosa and in 53.92%of ESCC samples(P<0.05).The expression level of GST-πwas also significantly higher in welldifferentiated carcinomas(65.63%)than in poorlydifferentiated carcinomas(35.00%,P<0.05). CONCLUSION:The expression of TS and of GST-πmay be used as molecular markers for the characterization of ESCC.Poorly-differentiated cells showed increased expression of TS and reduced expression of GST-π. AIM: To investigate the expression of thymidylate synthase(TS) and glutathione-s-transferaseπ(GST-π) in esophageal squamous cell carcinoma and their association with the clinicopathologic characteristics. METHODS: Immunohistochemical methods were used to detect the expression of TS and GST -πin surgically resected formalin-fixed, paraffin-embedded esophageal squamous cell carcinoma (ESCC) tissue sections from 102 patients(median age,58 years)and in 28 normal esophageal mucosa(NEM)samples.The relationship between TS and GST-πexpression and The clinicopathologic factors was examined. RESULTS: The expression of TS and GST-πwas not strongly ly significantly associated with age of the patients, tumor size, lymph node metastasis, depth of invasion or tumor stage. TS staining was positive in 17.86% of normal esophageal mucosa And in 42.16% of ESCC samples(P<0.05).The expression level of TSwas not only significantly lower in well-differentiated (21.88%)than in poorly-differentiated carcinomas (51.43%,P< 0.05), but was also significantly higher in samples from male patients (46.51%) than from female patients (18.75%, P<0.05). GST-πwas positively stained in 78.57% of normal esophageal mucosa and in 53.92% of ESCC samples ( P<0.05).The expression level of GST-πwas also significantly higher in welldifferentiated carcinomas(65.63%)than in poorly differentiatent carcinomas(35.00%,P<0.05). CONCLUSION: The expression of TS and of GST-πmay be used as molecular Marker for the characterization of ESCC.Poorly-differentiated cells showed increased expression of TS and reduced expression of GST-π.