4728 Classification of gastric stromal tumor according to immunohistochemical phenotype.

Abstract

Backgrounds: Gastrointestinal stromal tumor(GIST) is a mesenchymal tumor which originates from the GI tracts. Although recent immunohistochemical study has helped classifying mesenchymal tumor and forming diagnostic criteria for benign and malignant tumors according to cell's origin and differentiation, it is yet to be settled. This study has classified gastric stromal tumor by using immunohistochemical staining. Materials and Methods: Immunohistochemical staining was performed on the gastric stromal tumor specimens attained by endoscopic resection and surgery. Smooth muscle actin, Desmin, Neuron-specific enolase, S-100, CD 34 and Vimentin has been used as immunohistochemical antibodies and the guideline for Ackerman's surgical pathology has been used as criteria for diagnosing malignancy(Ackerman's surgical pathology 8th ed, 1996). Smooth muscle type was classified as benign, borderline and malignant according to the size and number of mitosis. Neural type was classified as malignant, and combined smooth muscle-neural type and uncommitted type were classified as either potentially malignant or malignant. Results: Subjects consisted of 12 males and 26 females with average age being 53 ± 12.8 years old. 22 cases has been endoscopically resected, 16 surgically removed, with the mean length of tumor being 25.3 ± 18.1 mm. The results of immunohistochemical staining showed 12 cases(31.6%) of smooth muscle type, 7 cases(18.4%) of neural type, 1 case(2.6%) of combined smooth muscle-neural type and 18 cases(47.4%) of uncommitted type. On the basis of above immunohistochemical results and histologic findings, 12 cases(31.6%) were regarded as benign, 17 cases(44.7%) as potentially malignant or malignant, and 9 cases(23.7%) as malignant(Table). Conclusion: When classified by immunohistochemical staining, 68.4% of gastric stromal tumor proved to be potentially malignant or malignant.