2040 Where Can the Lesion Be? A Pelvic GIST With Both a Normal Upper and Lower Endoscopy

Abstract

INTRODUCTION: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the GI tract; the age-adjusted incidence is 6.8 per million in the SEER data collected from 1992-2000 [1]. CASE DESCRIPTION/METHODS: An 80-year-old female with history of CVA, hypertension, diabetes, hyperlipidemia, diverticulosis, and mild antral gastropathy with negative H.Pylori presented to the hospital with syncope and two episodes of dark stools mixed with bright red blood. Physical exam revealed normoactive bowel sounds and tenderness to palpation in the left lower quadrant without rebound tenderness. A rectal exam was positive for melena but negative for any palpable masses or hemorrhoids. Initial laboratory workup showed a hemoglobin of 4.8 and elevated BUN to 60 from a baseline of 40. Patient was fluid resuscitated and given packed red blood cells with appropriate response to transfusion; the patient remained hemodynamically stable and had no further episodes of hematochezia. On endoscopic investigation, both upper and lower endoscopy were unremarkable and did not reveal any lesions; colonoscopy showed old blood but no active bleeding. An Abdominopelvic CT scan was performed which showed a 9.5 × 9.8 cm soft tissue mass in the right abdomen inferior to the liver and a 12.5 × 12.4 cm conglomerate soft tissue mass in the right pelvis as well as a 1.3 cm left hepatic hypodensity concerning for liver metastasis (Figure 1). Core biopsy of the pelvic mass revealed spindle cells and positive KIT (CD 117) consistent with GIST (Figures 1 and 2). DISCUSSION: GISTs are commonly are found in the stomach and proximal small intestine, but they can be found in any part of the gastrointestinal tract. GISTs are composed of spindle (70%) or epithelioid (30%) cells, and 10%-30% are malignant showing intra-abdominal spread or liver metastases. Most GISTs will be positive for a KIT protooncogene mutations leading to uncontrolled activation of KIT (CD 117), a receptor tyrosine kinase (RTK) [2]. The likelihood of metastasis increases when the tumor reaches a size of 10 cm. Tumors located in the small intestines have more potential of metastasis than gastric tumors due to delay in onset of symptoms. While endoscopic investigation is a significant diagnostic method, some cases may yield unremarkable findings. Our case highlights the importance of obtaining further imaging studies when no source of gastrointestinal bleed or mass can be identified on initial endoscopy.