Background/aim: Gastrointestinal stromal tumors (EGIST) are mesenchymal tumors which may originate in sites outside the gastrointestinal tract with clinico-pathological and molecular profiles similar to GISTs. Here is a series of case reports from The National Cancer Institute (INCA) about this rare type of tumor.
Methodology: We retrospectively analyzed 142 patients with a diagnosis of GIST who were treated at INCA between 1997 and 2009, among which 9 were confirmed as having EGIST.
Results: We identified 9 patients with a diagnosis of EGIST, 7 of which (77.8%) were female patients with an average age of 56.8 (36-81) years. All patients were symptomatic, with abdominal pain present in 55% of cases. The tumors were located in the pancreas (n=2), in the retroperitoneum (n=3), and in the mesocolon, in the mesentery of the small intestine, in the spleen and in the pelvis (all n=1), respectively. The average tumor size was 18(8.5-27)cm. Immunohistochemistry revealed CD 117 positive in 100% of cases and CD34 positive in 62.5%. Five patients were treated surgically, three of which were submitted to R0 resection. Among those patients, all recurred after 31, 23 and 17 months respectively, and the most frequent sites were the liver and the peritoneum. Out of these three recurrences, two were "rescued" surgically (66%). Five patients were given imatinib (three patients considered unresectable, one submitted to R2 resection and another patient with recurrent disease not amenable to surgery) two patients did not receive any treatment due to compromised clinical conditions. The average overall survival was 26.4 (04-114) months.
Conclusion: The occurrence of EGIST is extremely rare and little is known about their actual origin. They manifest through bulky masses, which compromise the prognosis. Aggressive surgical intervention is the most effective treatment associated with the use of imatinib, and a strict followup is necessary due to high recurrence rates.