GOAL: This study concerns the new anatomo-pathologic semantics of the ancient gastric leiomyoblastoma that become gastric stromal tumors (GST) and identified as stemming of "pace-maker" cells of Cajal related to the immunohistochemical characterization of the phenotype. MATERIAL: and methods. We limited the study to the mesenchymatous tumors to "pacemaker" cells. For this purpose, we report four documented observations of gastric stromal tumors correlated to the histology and to the immunohistochemical study. RESULTS: Although some signs are often described (exogastric development, heterogeneity with cystic and necrotic component, predominating peripheral enhancement...), radiological aspects of these tumors are not specific because, analogues to the other mesenchymal tumors (leiomyoma or schwannoma). The topographic diagnosis is difficult, realized by echoendoscopy, CT scan and MRI. The irregularity of contours evokes the malignancy as hemoperitoneum. GST do not show lymphophilic behavior that differentiates them from the adenocarcinomas and gastric lymphomas. The surgical treatment is the best treatment, allowing the immuno-histological diagnosis of certainty from the complete operative specimen. CONCLUSION: Some tumors are difficult in classifying despite classic histology necessitating immunohistochemical tests for the identification of muscular, nervous, autonomous nervous system flexion of mesenchymatous tumors with epithelioid or spindle cells of the gastrointestinal tract. Then a radio-clinical follow-up is therefore indicated: the evolution is the alone real marker of malignancy.