A histological,ultrastructural and immunohistochemical study of gastrointestinal stromal tumors

Purpose: To further study the histogenesis and pathological diagnosis of gastrointestinal stromal tumors (GISTs). Methods: Eighteen cases of GISTs of stomach (12), small bowel (5) and rectum (1) were examined by light microscopy, electron microscopy and immunohistochemistry. Results: Eighteen cases showed morphological features with elongated spindle cells. Ultrastructurally, three cases presented with smooth muscle differentiation and one case presented with neural element differentiation. Fourteen cases lacked differentiation. Immunostainings were positive for CD117(18/18), CD34(16/18), SMA(1/18) and S 100(2/18). All cases were negative for desmin and NSE. Thirteen malignant GISTs and five benign GISTs were diagnosed. Conclusion: GISTs was a group of independent tumors with their own characteristics. CD117 was a sensitive and specific marker for GISTs. The diagnosis of benign or malignant GISTs should be made by taking into account of various factors including morphological and ultrastructural features. Benign GISTs still required long term follow up.