S3032 Extra-Gastrointestinal Stromal Tumor (EGIST): An Unusual Case of Worsening Exertional Dyspnea

Abstract

INTRODUCTION: Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors of the gut. GISTs are rare, composing 0.1-3% of all gastrointestinal tumors. Exceedingly rare cases of GISTs have been identified outside of the GI tract and named extra-gastrointestinal stromal tumors (EGISTs). Here, we present a case of a large EGIST with multiple metastasis that initially presented with worsening exertional dyspnea. CASE DESCRIPTION/METHODS: An 83-year-old female with past medical history significant for hypertension and breast cancer status post lumpectomy and radiation therapy presented with worsening shortness of breath on exertion for 6 weeks. She also reported mild left upper quadrant abdominal pain, weakness, and decreased appetite. On physical exam, her abdomen was distended with splenomegaly noted. CTA of the chest shows right-sided pulmonary emboli without right ventricular strain and intra-abdominal ascites with a markedly enlarged spleen. US of lower extremities was positive for right femoral deep vein thrombosis. The patient was placed on heparin drip, which was later changed to Lovenox. Abdominal US shows multiple intrahepatic lesions and epigastric mass. CT of the abdomen and pelvis shows a large mass occupying a majority of the abdominal and pelvic cavities and multiple metastasis noted to liver and adrenal glands. Core biopsy of the abdominal mass showed high grade (Grade 2, x > 5 mitotic figures per 5 mm) GIST with necrosis. Tumor cells were positive for DOG1, CD117, and CD34. EGD revealed antral gastritis with biopsy positive for H. pylori. She was discharged and placed on Imatinib with repeat imaging after several months of Imatinib to evaluate for possible resection of disease. DISCUSSION: EGISTs are rare mesenchymal tumors that have been identified in the retroperitoneum and pelvis. GISTs result from activating mutations of proto-oncogenes c-KIT (CD117) or PDGFR-alpha. These activated proto-oncogenes increase tyrosine kinase receptor activity and result in stem cell proliferation. Roughly one third of GISTs have malignant potential and are prone to metastatic spread. GIST prognosis is multifactorial, depending on tumor size, mitotic potential, and metastatic invasion. Imatinib, a tyrosine kinase inhibitor, is the first-line therapy of metastatic GIST. In addition, surgical resection is the mainstay of therapy, especially in cases where the lesion is > 2 cm. In the 3 to 5 years post-treatment, close surveillance is warranted due to high risk of GIST recurrence.Figure 1.: Abdominal and Pelvic GIST on CT of the abdomen and pelvis.Figure 2.: Abdominal and Pelvic GIST on CT of the abdomen and pelvis.