AIM:To investigate the clinicopathologic features of patients with extra-gastrointestinal stromal tumors(EGISTs)in South Korea.METHODS:A total of 51 patients with an EGIST were identified.The clinicopathologic features,including sex,age,location,tumor size,histology,mitotic rate,immunohistochemical features,genetic status and survival data,were analyzed.RESULTS:The median age was 55 years(range:29-80years),and male:female ratio was 1:1.04.The most common site was in the mesentery(n=15)followed by the retroperitoneum(n=13)and omentum(n=8).The median tumor size was 9.0 cm(range:2.6-30.0cm)and the median mitotic rate was 5.0/50HPF.(1/50-185/50).KIT was analyzed in 16,which revealed 10cases with wild-type KIT and 6 cases with an exon 11mutation.Among 51 patients,31 patients had undergone surgery,and 10 had unresectable disease and had taken palliative imatinib,which resulted in 22.7 mo of progression-free survival.Of the patients who had undergone surgery,18 did not take adjuvant imatinib,and 8 of these were categorized as“high risk”according to the risk criteria.However,the relapse-free survival was not different(P=0.157)between two groups.CONCLUSION:Because the biologic behaviors of GISTs differ according to the location of the tumor,a more stratified strategy is required for managing EGISTs including incorporation of molecular features. AIM: To investigate the clinicopathologic features of patients with extra-gastrointestinal stromal tumors (EGISTs) in South Korea. METHODS: A total of 51 patients with an EGIST were identified. Including clinicopathologic features, including sex, age, location, tumor size, histology , mitotic rate, immunohistochemical features, genetic status and survival data, were analyzed .RESULTS: The median age was 55 years (range: 29-80years), and male: female ratio was 1: 1.04. the most common site was in the mesentery (n = 15) followed by the retroperitoneum (n = 13) and omentum (n = 8) .The median tumor size was 9.0 cm (range: 2.6-30.0 cm) and the median mitotic rate was 5.0 / 50 HPF. 50-185 / 50) .KIT was analyzed in 16, which revealed 10cases with wild-type KIT and 6 cases with an exon 11mutation. Among 51 patients, 31 patients had undergone surgery, and 10 had unresectable disease and had taken palliative imatinib, which resulted in 22.7 mo of progression-free survival. Of the patients who had undergone surgery, 18 did not take adjuvant imatinib, and 8 of these were categorized as “high risk ” according to the risk criteria. Despite, the relapse-free survival was not different (P = 0.157) between two groups. CONCLUSION: Because the biologic behaviors of GISTs differ according to the location of the tumor, a more stratified strategy is required for managing EGISTs including incorporation of molecular features.