[720] The Usefulness of New Preparatory Procedures for EUS-FNAB To Diagnose Gastrointestinal Stromal Tumor.

Tomoko Wakasa, Kumiko Inayama, Kenichi Wakasa, Masahiko Ohsawa, Yoshihiro Okabe, Yukio Osaki. Osaka Red Cross Hospital, Japan; Osaka City University Graduate School of Medicine, Japan

Background: Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) is very useful for the diagnosis of submucosal tumor of the stomach. At present, immunohistochemical staining is necessary to diagnose and confirm the malignant potential of mesenchymal tumors. However, the preparation of a sufficient amount of a paraffin-embedded block is often difficult, because samples often contain a large amount of blood. The bloody contents make it difficult to detect the tumor or interpret the results of immunohistochemistry. We herein established a new preparatory method using culture medium for EUS-FNAB specimens and evaluated its utility.
Design: Between October 2008 to August 2010, 24 patients diagnosed with a submucosal tumor of the stomach and 2 patients with that of the duodenum underwent EUS-FNAB. Specimens were obtained by physicians using EUS with a 22-gauge needle. All specimens were immediately put into 10 ml of culture medium in a Petri dish (Hanks solution, Nissui Pharmaceutical, Tokyo, Japan). The dish was transferred to the laboratory, and then we separated tissue samples and mucus from the clot. The tissue samples were put into a fine mesh bag, and were processed routinely for paraffin sections and HE staining. After the pathologist diagnosed the tumors based on HE staining, immunohistochemical staining for c-kit (CD117), CD34, smooth muscle actin, Ki-67, and S-100 was performed for mesenchymal tumors.The reactivity for each immunohistochemical stainings was compared with tissues from surgically resected specimens.To evaluate the volume of the collected tissue samples, the area of positive staining for c-kit was measured using on image analyzing system (WinROOF, Mitani Co., Tokyo, Japan).
Results: Sixteen cases were diagnosed as GIST and 3 cases as adenocarcinoma, 6 cases as ectopic pancreas, and 1 case as schwannoma. All cases involved a high yield of tissues, and so we could diagnose them histologically. Among them, 10 cases of GIST, 1 case of adenocarcinoma, and 1 case of schwannoma were operated on. In all 10 surgically resected cases of GIST, the diagnoses and the immunoreactivity of EUS-FNAB specimens were consistent with those based on surgical specimens. In 16 GISTs, the average area of c-kit-positive tissue was 5.15 mm2 (2.1 to 9.7) in paraffin-embedded specimens.
Conclusions: Our methods using culture medium ensure a sufficient amount of histological specimens for immunohistochemical staining.
Category: Gastrointestinal

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 164, Tuesday Morning

 

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