Endoscopic ultrasound-guided fine-needle aspiration cytology in the diagnosis of the gastrointestinal stromal tumor of the stomach.

Background This study aims to evaluate the usefulness of endoscopic ultrasound-guided fine-needle aspiration cytology (EUS-FNAC) in the diagnosis of the gastric gastrointestinal stromal tumor (GIST). Methods We retrospectively investigated the efficacy and accuracy of EUS-FNAC in the diagnosis of gastric GIST. Cytological smears and cytoblock sections including immunohistochemistry and mutational studies from patients diagnosed as gastric GISTs were retrieved. Results Thirty patients (mean age 68.8 years, range 32-88 years, Male:Female 1:1.7) were diagnosed by cytological and cytoblock study to have GIST. The size of tumors ranged from 1.6 to 25 cm (mean 6.0 cm). 7 (23%) cases were incidentally discovered. Location was: gastric body 13 (43.3%), fundus 8 (26.7%), antrum 7 (23.3%), cardia 2 (6.7%). The study of removed tumors was correlated with the cytological findings. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 75%, 100%, 100%, 46%, and 96%. There were no false-positive cases. The preoperative risk assessment of 27 cases with cytoblock were: none 3 (11.1%), very low 8 (29.6%), low 12 (44.4%), high 3 (11.1%), insufficient clinical data 1 (3.7%). The follow-up varied from 2 to 120 months (mean 46.7 months). Only 1 patient of the high-risk group died. The most frequent mutations found were those of c-KIT in exon 11. Conclusions Pathological diagnosis was based on a combination of cytological, histopathological, and immunohistochemical features. EUS-FNAC is a reliable, accurate, and safe method for the diagnosis of GIST. The cytoblock allows tumor risk classification and mutational study of the cases.