Objective:To investigate the clinical and pathologic morphological features

immunohistochemical speciality of the gastrointestinal stromal tumors(GISTs) and their histogenesis

treatment and prognosis as well.Methods:The morphologic characteristics of GISTs were studied in 51 cases using light microscopy.The expression of c-kit(CDll7)

CD34

vimentin

actin

S-100 were detected in all the cases with SP immunohistochemistry staining.Results:Among 51 cases of GISTs

40 were spindle cell type

4 epithelioid cell type and 17 mixturetype.Almost all of the stromal tumors were strongly positive for vimentin(99%)

48 out of 51 tumors positive for CD117 (c-kit)(95.0 %) and 41 positive for CD34(78.5%).Some cases also expressed actin

S-100.Conclusion:GISTs are the most frequent mesenchymal tumor seen in the gastrointestinal tract.Under light microscope

the morphology of stromal tumors looks sometimes like that of a leiomyoma and Schwannoma.Application of immunohistochemical markers (particularly CD117 and CD34)is considered necessary for the differential diagnosis.GISTs may originate from the pluripotential stem cell of the interstium.