To analysis the clinicopathologic and immunohistochemical features of gastrointestinal stromal tumor and external gastrointestinal stromal tumor

Objective:To study the clinicopathologic and immunohistochemical characteristics of gastrointestinal stromal tumors(GIST) and external gastrointestinal stromal tumors(EGIST).Methods:The morphologic features in 20 cases of GISTs and EGISTs were observed under light microscopy. The expressions of CD117,CD34,Vimentin,SMA,desmin and S-100 were detected by immunohisto-chemical SP method.Results:In 20 cases of GISTs,age mean 59.82 years(range from 27 to 80 years),female 11 cases and male 9 cases. The tumors were situated in stomach(8 cases),in small intestine(4 cases),in large intestine(2 cases),in esophagus(one case),in mesenterium(4 case) and in omemtum(one case). The tumors were mainly composed of spindle cells and epithelioid cells,arranged in pallisading,interlacing fasicles,whirling,cellular clusters,et al. The positive rates of CD117,CD34,Vimentin,SMA,desmin and S-100 in 20 cases were 95%(19/20),75%(15/20),100%(20/20),40%(8/20),5%(1/20) and 25%(5/20) respectively. The most common symptoms were abdomen mass,discomfort and gastrointestinal hemorrhage. Three cases were benign,four cases potential malignant and 13 cases malignant. Mitotic activity over 5/50 HPF,tumor cell necrosis and high tumor cellularity had significant differences among three groups.Conclusion:GIST predominantly occurred in older patients. There were not different between female and male cases. GIST seems to occur most frequently at gastrointestinal tract. The tumor cells had varied arrangements and multiple differentiated characteristic. Immunostaining suggested that only some of the GISTs showed partial differentiation toward smooth muscle,neuron or both. Mitotic activity over 5/50 HPF,high tumor cellularity and tumor necrosis were the helpful parameters for judgement of malignancy. CD117 and CD34 were the more specific and sensitive antibody in diagnosis of GISTs. Immunohistochemisty plays an important role in the pathological diagnosis and differential diagnosis of GISTs.