[629] Endoscopic Ultrasound (EUS)-Guided Fine Needle Aspiration (FNA) Cytology of Gastrointestinal Stromal Tumors: A 15-Year Retrospective Study of 104 Cases

CJ Mills, NP Agaram, JM DeWitt, HM Cramer. Indiana University School of Medicine, Indianapolis, IN

Background: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Due to their submucosal location within the GI tract, they are difficult to diagnose by conventional surgical biopsy techniques. EUS-guided FNA has been increasingly used for the preoperative diagnosis of GISTs. In reviewing our experience, our aim in this study is to determine the accuracy of EUS-guided FNA for the diagnosis of GIST.
Design: A computerized search of the cytopathology laboratory information system was performed and all cases in which a diagnosis of GIST was rendered or suggested by FNA were identified. All correlating surgical pathology reports were obtained and all cytology slides and correlating surgical pathology slides were retrospectively reviewed.
Results: Over a 15-year period, a total of 104 EUS-guided FNA cases were diagnosed as GIST or as a spindle cell neoplasm in which GIST was in the cytologic differential diagnosis. The patients included 57 males and 47 females with a mean age of 65 and an age range of 21 to 93 years. Gastric GISTs accounted for 75 of the 104 cases (72%). The tumors ranged in size from 0.6 to 15.0 cm (mean: 4 cm). The cytomorphologic diagnosis of GIST was supported by positive c-kit immunostaining performed on either cell block sections or follow-up surgical biopsy in 57 patients (55%). Two cases that were negative for c-kit had no additional follow-up. Histologic follow-up was available for 50 patients (48%). Follow-up histologic diagnoses other than GIST were found in 6 cases: leiomyosarcoma (1 case), leiomyoma (2 cases), synovial sarcoma (1 case), neurofibroma (2 cases). Of 48 patients with available clinical follow-up 12 (25%) were found to have developed metastases.
Conclusions: EUS-guided FNA, along with confirmatory c-kit immunostaining, is an accurate method of establishing a preoperative pathologic diagnosis of GIST. In our study, all subclassification errors occurred in cases in which confirmatory immunostaining could not be performed due to hypocellularity of the sample.
Category: Gastrointestinal

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 116, Tuesday Afternoon