Abstract: Objective  To investigate the clinical and pathological features of primary extragastrointestinal stromal tumors (EGISTs) and analyze the potential prognostic factors.  Methods　The EGISTs patients admitted to Guangdong Provincial People's Hospital from January 2006 to August 2017 were analyzed. All cases underwent surgical resection of the tumor and further pathological diagnosis. All patients were followed up.　Results　A total of 15 patients who were pathologically confirmed as EGISTs were collected in 11 years. Among the 15 patients, 11 were male and 4 were female, with the average median age of onset was 45 years (33~70 years). In the clinical manifestations, the most initial symptoms were abdominal mass. As for tumor location, retroperitoneum (4 cases), mesocolon (4 cases), small intestinal mesentery (3 cases), pelvic cavity (1 case), left pleural cavity (1 case), pancreatic capsule (1 case), and lesser omentum (1 case) were observed. The median follow-up time was 53 months on average (ranged 1~102 months). Immunohistochemical report showed that CD117 of 14 cases positive expression(14/15), CD34 of 10 cases positive (10/15), DOG-1 of 6 cases positive (6/8). 7 patients received gene detection, while 2 cases found c-KIT gene exon 9 mutation, 2 cases c-KIT gene exon 11 mutation, 1 cases PDGFRa gene exon 12 mutation, 2 cases without any c-KIT gene or PDGFRa gene mutation. According the standard of reformative National Institutes of Health to classify the risk, five high-risk patients received R0 postoperative adjuvant imatinib therapy (average survival time was 67 months), while eight high-risk patients did not receive adjuvant therapy (average survival time was 36.58 months). Eight patients had appeared recurrence metastasis during follow-up, and eight patients had occurred tumor-related death.  Conclusions  Extragastrointestinalstromal tumors, whose most common symptom is abdominal mass, have low incidence and poor prognosis. The pathological features of EGISTs are similar to those of gastrointestinal stromal tumors (GISTs). R0 resection is the crucial treatment, and adjuvant imatinib therapy is beneficial to improve prognosis and prevent recurrence metastasis. 

Key words: Extragastrointestinalstromal tumors, 　EGISTs, 　Imatinib