1. Gastrointestional Stromal Tumors (GIST)

2. Gastrointestional Stromal Tumors (GIST) Anatomy of Gastric wall and grossly appearance of Gastric Tumors Adenocarcinoma GIST : gross and microscopic appearance

4. Histologic consideration Until 1990, GIST were all regard as smooth muscle nature and designated as leiomyoma, leiomyosarcomas when compose of spindle cell and leiomyoblastoma when compose of epithelioil cell With immunohistochemical and ultrastructural studies, they can be divided into 4 major categories Differentiation Pathway Immunohistochemical Benign Malignant 1.Smooth muscle cells smooth muscle actin √ √ desmin, myosin 2.Neural elements neuro specific enolase √ √ (NSE), S-100 protein 3.Smooth muscle and both 1,2 √ √ neural element 4.No differentiation C-kit protein CD117, all should be toward either cell type CD34 considered as Are thought to arise from potentially interstitial cell of Cajal malignant or malignant

5. Determination of malignant potential and prognosis I. Base on tumor size and mitotic activity Risk Size (cm) Mitotic count/50 HPF Very low <2 <5 } may be considered benign Low 2-5 <5 } Intermediate <5 6-10 } 5-10 <5 } potentially malignant High >5 >5 } or malignant >10 any } any >10 } II. Other negative prognostic factors: Positive resection margin, tumor rupture, distal location, high cellularity, tumor necrosis, presence of metastases or invasion to adjacent organ and mutation of c-kit gene. Note: No standard TNM staging system for GIST

7. Ultrasound CT Scan