AIM: To study the endoscopic, pathological and immuno-histochemical features of esophageal mesenchymal tumors. METHODS: Twenty-nine patients diagnosed as esophageal mysenchymal tumors by electronic endoscopy and endoscopic ultrasound (EUS) were observed under light microscopes, and all tissues were stained by the immunohistochemical method. The expression of CD117, CD34, SMA and desmin were measured by staining intensity of cells and positive cell ratios. RESULTS: Endoscopically, esophageal gastrointestinal stromal tumors (GISTs) and leiomyomas (LMs) had similar appearances, showing submucosal protuberant lesions. They all showed low echo images originated from the muscularis propria or muscularis mucosa on EUS. Endoscopy and EUS could not exactly differentiate esophageal GISTs from LMs. Microscopically, there were two kinds of cells: spindle cell type and epitheloid cell type in esophageal GISTs. Leiomyomas and leiomyosarcomas were only of spindle cell type. One malignancy was found in five cases of esophageal GISTs, and one malignancy in 24 cases of leiomyomas and leiomyosarcomas. Using Fisher’s exact method, the differences of malignant lesion proportion were not significant between esophageal LMs and GISTs, 1/5 vs 1/24 (P > 0.05). All cases of esophageal GISTs were positive for CD117, and 3 cases were also positive for CD34. The 24 cases of leiomyomas and leiomyosarcomas were all negative for CD117 and CD34. The differences of positive rates of CD117 and CD34 were significant between esophageal GISTs and LMs, 5/5 vs 0/24, 3/5 vs 0/24 (P < 0.005). All leiomyomas and leiomyosarcomas were positive for SMA, and desmin. Among 5 cases of esophageal GISTs, 2 cases were SMA positive, and 1 case was desmin positive. The differences in positive rates and expression intensity of SMA and desmin were significant between esophageal LMs and GISTs, 24/24 vs 2/5, 24/24 vs 1/5 (P < 0.005). CONCLUSION: The most common esophageal mesenchymal tumors are leiomyomas, and esophageal GISTs are less common. Most of esophageal LMs and GISTs are benign. Endoscopy and EUS are the effective methods to diagnose esophageal mesenchymal tumors and they can provide useful information for the treatment of these tumors. However, they cannot exactly differentiate esophageal GISTs from LMs. Pathological, especially immunohistochemical features are useful to differentiate GISTs from leiomyomas. AIM: To study the endoscopic, pathological and immuno-histochemical features of esophageal mesenchymal tumors. METHODS: Twenty-nine patients diagnosed as esophageal mysenchymal tumors by electronic endoscopy and endoscopic ultrasound (EUS) were observed under light microscopes, and all tissues were stained by the expression of CD117, CD34, SMA and desmin were measured by staining intensity of cells and positive cell ratios. RESULTS: Endoscopically, esophageal gastrointestinal stromal tumors (GISTs) and leiomyomas (LMs) had similar appearances, showing submucosal protuberant lesions They all showed low echo images originated from the muscularis propria or muscularis mucosa on EUS. Endoscopy and EUS could not exactly differentiate esophageal GISTs from LMs. Microscopically, there were two kinds of cells: spindle cell type and epitheloid cell type in esophageal GISTs. Leiomyomas and leiomyosarcomas were only of spindle cell type. One malignancy was found i Five cases of esophageal GISTs, and one malignancy in 24 cases of leiomyomas and leiomyosarcomas. Using Fisher’s exact method, the differences of malignant lesion proportion were not significant between esophageal LMs and GISTs, 1/5 vs 1/24 (P> 0.05) . All cases of esophageal GISTs were positive for CD117, and 3 cases were also positive for CD34. The 24 cases of leiomyomas and leiomyosarcomas were all negative for CD117 and CD34. The differences of positive rates of CD117 and CD34 were significant between esophageal GISTs and All leiomyomas and leiomyosarcomas were positive for SMA, and desmin. Among the 5 cases of esophageal GISTs, 2 cases were SMA positive and 1 The differences in positive rates and expression intensity of SMA and desmin were significant between esophageal LMs and GISTs, 24/24 vs 2/5, 24/24 vs 1/5 (P <0.005). CONCLUSION: The most common esophageal mesenchymal tumors are leiomyomas, and esophageal GIMost of esophageal LMs and GISTs are benign. Endoscopy and EUS are the effective methods to diagnose esophageal mesenchymal tumors and they can provide useful information for the treatment of these tumors. However, they can not exactly differentiate esophageal GISTs from LMs. Pathological, especially immunohistochemical features are useful to differentiate GISTs from leiomyomas.