EP34.02: Clinical and ultrasound features of extra gastrointestinal stromal tumours (eGIST)

To describe the clinical and sonographic characteristics of extra-gastrointestinal stromal tumours (eGISTs). This is a retrospective multicentric study. From the database of 9 large European gynecologic oncology centres we identified patients with a histological diagnosis of eGIST, who had undergone preoperative ultrasound. One author from each centre reviewed stored images and ultrasound reports, and described the lesions using IOTA and MUSA nomenclatures. In addition, clinical information, surgical and pathological reports were recorded. 35 women with eGISTs were identified, 17 incidental findings and 18 symptomatic cases. Median age was 57 years (range 21-85). Two patients (6%) had ascites and median CA 125 was 23 U/mL (range 7-403 U/mL). The vast majority of eGISTs were intraperitoneal lesions (33/35, 94%) with few retroperitoneally (2/35, 6%). The most common site was abdomen (23/35, 65.7%), and 12 lesions (34%) were in the pelvis. eGISTs were typically large (median of 79 mm) and solid tumors (31/35, 89%), the remaining eGISTs were multilocular-solid tumors (4/35, 11%). The tumour shape was mainly lobulated (20/35, 57%) or irregular (10/35, 29%). The echogenicity of solid tumours was less often uniform (8/35, 23%) but always hypoechogenic. More frequently solid tumours were non-uniform due to mixed echogenicity (13/27, 40%) or small irregular cysts (14/27, 37%). eGISTs were typically richly vascularised (colour score 3 and 4, 31/35, 89%) with no shadowing (31/35, 89%). Based on pattern recognition, eGISTs were usually correctly classified as malignant lesion (32/35, 91%) and the specific diagnosis of eGIST was the most frequent among the presumed diagnosis (16/35, 46%). On ultrasound, eGISTs were usually solid non-uniform intraperitoneal tumors of mixed or cystic echogenicity with rich vascularisation and no shadowing. They may mimic ovarian fibroma or uterine fibroids but the extra-genital origin in the combination with ultrasound characteristics in experienced hands point to the diagnosis of these uncommon tumours. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.