2739 A Rare Case of Multifocal Gastrointestinal Stromal Tumor

Abstract

INTRODUCTION: Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors most often located in the stomach and proximal small bowel although they can occur in any part of the gastrointestinal tract and occasionally in omentum, mesentery, and peritoneum. GISTs are traditionally thought of as solitary tumors that rarely present with multiple lesions. We present a unique case of multifocal GIST that was incidentally found on imaging. CASE DESCRIPTION/METHODS: A 44-year old woman with no prior medical history presented to the emergency department with a one-day history of left lower quadrant abdominal pain. A CT scan of abdomen and pelvis demonstrated acute diverticulitis, and incidentally a 6.2-cm heterogeneously enhancing exophytic mass along the inferior margin of the gastric body was seen. In addition, two lesions measuring 3.4 cm and 1.1 cm were seen adjacent to the gastrohepatic ligament (Figure 1). The patient’s abdominal pain improved with intravenous antibiotics. Gastroenterology was consulted given the mass lesions, and an endoscopic ultrasound was performed which showed three distinct heterogeneously hypoechoic masses (Figure 2), and fine needle biopsy (FNB) was performed. All three lesions were biopsied using three separate needles to avoid cross-contamination. Pathology of all three lesions was consistent gastrointestinal stromal tumor (GIST). Immunohistochemical staining was positive for DOG1 (Figure 3). The patient has been established with medical oncology for neoadjuvant therapy with Imatinib. DISCUSSION: Many GISTs are incidentally discovered on imaging or endoscopy. They are more frequently associated with early satiety, bloating, and bleeding although larger tumors can cause pain and symptoms of obstruction. Multifocal GISTs are exceedingly rare, other than exceptions in pediatric population, metastatic spread and hereditary syndromes. Newer studies suggest patients with multifocal GISTs may actually have multiple primary GISTs rather than metastatic spread, and molecular characterization can allow for proper staging and treatment planning. Multifocal GISTs have also been reported in patients with neurofibromatosis (NF) type I. However, our patient did not have any symptoms or signs suggestive of NF. It is important for gastroenterologists to know that multifocal GISTs can present in adults, and if suspicion is high, all lesions should be evaluated individually, and smaller lesions should not be attributed to metastasis unless proven otherwise.