Abstract

Gastrointestinal stromal tumor (GIST) is known as considerable controversal tumor about it's histogenesis, differentiation and biologic behavior. It is traditionally regarded as smooth muscle tumor. To evaluate and clarify the origin of tumor, we performed immunohistochemical study of 23 cases of GIST on CD34 antigen, alpha-smooth muscle actin, S-100 protein, and compared the result with 4 cases of typical leiomyoma of GI tract. The results were as follows. CD34 antigen expression was noted in 21 cases (91.3%) of GIST, while typical leiomyoma was all negative. There were no difference of CD34 expression according to the biologic behavior. However, it's staining pattern was significantly different (p<0.05). Focal or multifocal expression was dominant in benign GIST (58.3%), while diffuse expression was dominant in malignant GIST (80%). Actin was expressed in 5 cases of benign GIST (38.5%) and 1 of malignant GIST (16.7%) focally. All typical leiomyoma showed diffuse strong positivity on alpha-smooth muscle actin. S-100 protein was expressed in 2 cases of benign GIST (16.7%) only. The pattern of CD34 expression was focal in the actin or S-100 protein positive cases. In conclusion CD34 antigen is useful marker in the separation of GIST, from typical smooth muscle tumor. Also it suggest that most GISTs are histogenetically primitive mesenchymal cell origin. However, CD34 expression was unrelated with biologic behavior of GIST.

• Keywords: CD34 antigen;Gastrointestinal stromal tumor;Leiomyoma