AIM:To investigate the significance of c-kit gene mutationin gastrointestinal stromal tumors (GIST).METHODS:Fifty two cases of GIST and 28 cases of othertumors were examined.DNA samples were extracted fromparaffin sections and fresh blocks.Exons 11,9 and 13 ofthe c-kit gene were amplified by PCR and sequenced.RESULTS:Mutations of exon 11 were found in 14 of 25malignant GISTs (56%),mutations of exon 11 of the c-kitgene were revealed in 2 of 19 borderline GISTs (10.5%),and no mutation was found in benign tumors.The mutationrate showed significant difference (x~2=14.39,P<0.01)between malignant and benign GISTs.Most of mutationsconsisted of the in-frame deletion or replication from 3 to48 bp in heterozygous and homozygous fashions,None ofthe mutations disrupted the downstream reading frame ofthe gene.Point mutations and frame deletions were mostfrequently observed at codons 550-560,but duplicationswere most concentrated at codons 570-585.No mutationsof exons 9 and 13 were revealed in GISTs,Neither c-kitgene expression nor gene mutations were found in 3leiomyomas,8 leiomyosarcomas,2 schwannomas,2malignant peripheral nerve sheath tumors,2 intra-abdominal fibromatoses,2 malignant fibrous histiocytomasand 9 adenocarcinomas.CONCLUSION:C-kit gene mutations occur preferentiallyin malignant GISTs and might be a clinically useful adjunctmarker in the evaluation of GISTs and can help todifferentiate GISTs from other mesenchymal tumors ofgastrointestinal tract,such as smooth muscle tumors,schwannomas,etc. AIM: To investigate the significance of c-kit gene mutationin gastrointestinal stromal tumors (GIST). METHODS: Fifty two cases of GIST and 28 cases of othertumors were observed. DNA samples were extracted fromparaffin sections and fresh blocks. Exons 11, 9 and 13 of the c-kit genes were amplified by PCR and sequenced .RESULTS: Mutations of exon 11 were found in 14 of 25 normalignant GISTs (56%), mutations of exon 11 of the c-kit gene were revealed in 2 of 19 borderline GISTs (10.5% ), and no mutation was found in benign tumors. The mutation rate showed significant difference (x ~ 2 = 14.39, P <0.01) between malignant and benign GISTs. Host of mutationsconsisted of the in-frame deletion or replication from 3 to 48 bp in heterozygous and homozygous fashions, None of the mutations disrupted the downstream reading frame of the gene. Point mutations and frame deletions were most frequently observed at codons 550-560, but duplicationswere most concentrated at codons 570-585. No mutations of exons 9 and 13 were revealed in GISTs , Neither c-kitgene expression nor gene mutations were found in 3leiomyomas, 8 leiomyosarcomas, 2 schwannomas, 2 normalignant peripheral nerve sheath tumors, 2 intra-abdominal fibromatoses, 2 malignant fibrous histiocytomas and 9 adenocarcinomas. CONCLUSION: C-kit gene mutations occur preferentially in malignant GISTs and might be a clinically useful adjunctmarker in the evaluation of GISTs and can help todifferentiate GISTs from other mesenchymal tumors ofgastrointestinal tract, such as smooth muscle tumors, schwannomas, etc.