Unusual metastases of gastrointestinal stromal tumor and genotypic correlates: Case report and review of the literature.

Abstract

Gastrointestinal stromal tumors (GISTs) are defined as mesenchymal tumors of the gastrointestinal tract and are characterized by positive CD117 staining, and in most cases positive CD34 staining, with compatible gross features and microscopic findings of a highly cellular mesenchymal tumor of the gastrointestinal tract composed of spindle cells, epithelioid cells or a combination of both (1). They are usually derived from a mutation of the KIT (CD117) or PDGFRA (platelet derived growth factor receptor alpha) gene. Distinguishing GIST from other mesenchymal derived tumors was historically a challenge, since both can arise from the interstitial cells of Cajal, or GI pacemaker cells that form the interface between the autonomic innervation and smooth muscle of the bowel wall (2). The distinction of GISTs based on molecular etiology was described by Hirota et al in 1998, with discovery of a mutation in c-KIT encoding a pro-oncogenic receptor tyrosine kinase (KIT) (3). It is estimated that 4500 to 6000 new cases of GIST are diagnosed in the United States annually and most occur in the stomach (50%-70%) or small intestine (20%-30%) (4). GISTs are often asymptomatic and discovered incidentally during surgery, endoscopic procedures, or imaging studies. However, the clinical presentation of some GISTs may include overt GI bleeding, abdominal mass, abdominal pain, or bowel obstruction and acute abdomen (2). The most common metastatic sites of gastrointestinal stromal tumors are the liver (65%) and peritoneum (21%); GISTs rarely metastasize to lymph nodes (6%), bone (6%), lung (2%) (2),(5), and soft tissue (less than 1%) (6),(7). We report the case of a female diagnosed with GIST with subsequent metastases to the liver, peritoneum, lung, bone, and soft tissue.