The tissue specimen obtained by EUS-FNA also stained positively for Pet1 (Figure4)

The tissue specimen obtained by EUS-FNA also stained positively for Pet1 (Figure4). Pet1 has been reported, even in KIT-negative GISTs. KIT-negative GISTs most commonly arise in the belly and are mainly characterized by epithelioid features Fangchinoline histologically. We describe our experience with a rare case of a KIT-negative GIST of the belly that was diagnosed by positive immunohistochemical staining for Pet1 in a patient who presented with severe anemia. Our findings suggest that immunohistochemical staining for Pet1, in addition to gene analysis, is useful for the diagnosis of KIT-negative tumors that are suspected Fangchinoline to be GISTs. Keywords:KIT Fangchinoline unfavorable, Gastrointestinal stromal tumors, Discovered on gastrointestinal stromal tumor-1, Platelet-derived growth factor receptor alpha Core tip:We describe our experience with a rare case of a KIT-negative gastrointestinal stromal tumor (GIST) of the belly that was diagnosed by positive immunohistochemical staining for Discovered on GIST-1 (Pet1) in a patient who presented with severe anemia. Our findings suggest that immunohistochemical staining for Pet1, in addition to gene analysis, is useful for the diagnosis of KIT-negative tumors that are suspected to be GISTs. == INTRODUCTION == A gastrointestinal stromal tumor (GIST) is usually a mesenchymal tumor derived from Fangchinoline the mesoderm that occurs in the gastrointestinal tract. The estimated incidence is usually 2 cases per 100000 people per year. The most common age at diagnosis is usually 50-60 years. KIT protein is usually characteristically expressed by immunohistochemical staining. Gain-of-function mutations of thec-kitgene (approximately 90%) or the platelet-derived growth factor receptor alpha (PDGFRA) gene (approximately 5%) are the major causes of GISTs[1]. Immunohistochemical staining and gene analysis are considered useful for diagnosis, but if the tumor is usually unfavorable for KIT, CD34, S-100, and easy muscle mass actin (SMA), a definitive diagnosis is usually often challenging. We describe our experience with a patient in whom immunohistochemical staining for Discovered on GIST-1 (Pet1) enabled Fangchinoline the diagnosis of a KIT-negative GIST[2]. == CASE Statement == A 60-year-old man was referred to the Department of Gastroenterology of our hospital because of wooziness, shortness of breath on effort, and tarry stools. A blood test showed that this hemoglobin level was 3.6 g/dL, indicating severe anemia. Upper gastrointestinal endoscopy disclosed a submucosal tumor accompanied by an ulcer with an adherent clot, arising in the superior portion of the anterior wall of the gastric antrum (Physique1). Endoscopic ultrasonography (EUS) revealed a well-demarcated, homogeneous, hypoechoic mass with a flat border. The mass was approximately 4 cm in diameter and arose from your fourth layer of the gastric wall (Physique2). Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB)[3,4] was performed to obtain a definitive diagnosis and showed aggregations of cells with spindle-like or polygonal nuclei. However, immunohistochemical staining was unfavorable for KIT, CD34, S-100, and SMA. A GIST was strongly suspected, but a definite diagnosis was not reached. Gene analysis could not be performed because the tissue sample was too small. However, the patient had a symptomatic, submucosal tumor with no distinct evidence of distant metastasis or direct invasion on enhanced computed tomography of the chest and abdomen. Surgery was, therefore, indicated according to the clinical practice guidelines for GIST in Japan[5], and a distal gastrectomy was performed. On macroscopic examination, the surgically resected specimen showed no evidence of bleeding or necrosis. The tumor measured 45 mm in diameter, and the resection margins were tumor negative. Histopathological examination showed that the tumor consisted of mixed components, including diffuse proliferations of spindle cells with eosinophilic cytoplasm, as well as epithelioid cells in some regions. One mitosis was found per 50 high-power fields, and the MIB-1 index was 3%. Immunohistochemical staining was negative for KIT, CD34, S-100, and SMA, but it was positive for vimentin and DOG1, a membrane channel protein (Figure3). The tissue specimen obtained by EUS-FNA also stained positively for DOG1 (Figure4). Genetic analysis showed a mutation in exon 18 (D842V) of thePDGFRAgene, with no mutation in thec-kitgene. On the basis of these results, a KIT-negative GIST with low risk according to Fletchers Rabbit Polyclonal to NPM classification[6], and very low risk according to Miettinens classification, was diagnosed[7]. The patient recovered uneventfully after surgery. As of 3 years after surgery, the patient has been followed up on an outpatient basis and remains free of metastasis and recurrence. == Figure 1. == Findings on upper gastrointestinal endoscopy. A submucosal tumor accompanied by an ulcer with an adherent clot was found in the superior.