Extragastrointestinal Stromal Tumor (EGIST): A 16-Year Experience of 13 Cases Diagnosed at a Single Center

BACKGROUND Gastrointestinal stromal tumor (GISTs) rarely occurs outside the GI tract as extragastrointestinal stromal tumor (EGIST). The aim of this study was to review the clinical presentation, diagnosis, and outcome of EGIST at a single center. MATERIAL AND METHODS The study was a retrospective study performed at Istanbul University Hospital in a 16-year period and included patients with a histopathological diagnosis of EGIST confirmed to arise outside the GI tract. The patients' available medical records included patient demographics, imaging and surgical data, and diagnostic histopathology reports. Cases of EGIST underwent follow-up for several years and the medical files of patients were well maintained. RESULTS Thirteen cases of EGIST included six women and seven men, with a mean age of 59.6 years (range, 33-83 years). Eleven patients had EGISTs located in the intra-abdominal cavity, one patient's tumor was in the retroperitoneum, and in the jejunal mesentery in one patient. The mean diameter of the EGISTs was 15.6 cm (range, 4-30 cm). Immunohistochemistry showed that all cases were negative for desmin, with positive immunostaining for CD34 (n=6), smooth muscle actin (SMA) (n=3), and Ki67 (n=6), without specific diagnostic markers. Following surgical resection, tumor recurrence occurred in three patients, and metastasis in two patients. The mean overall survival (OS) was 45.66 months (56.44 months for women; 32.57 months for men); the 5-year survival rate of our patients was 38%. CONCLUSIONS EGIST presented with a large tumor size at diagnosis, was mainly intra-abdominal, and had a low mean patient survival time with no specific diagnostic tissue immunomarkers.