A Case of Gastric Gastrointestinal Stromal Tumor with Platelet Derived Growth Factor Receptor Alpha Mutation

Hiroshi Nimura, Naoto Takahashi, Atsushi Watanabe, Sigeo Yamashita, Hironori Ohdaira, Toshihiko Shinohara, Katsutoshi Kobayashi, Norio Mitsumori, Hideyuki Kashiwagi and Katsuhiko Yanaga

Division of Digestive Surgery, Department of Surgery, The Jikei University School of Medicine

A 64-year-old man with a 9 cm gastric gastrointestinal stromal tumor (GIST) and plateletderived growth factor receptor alpha (PDGFR-alpha) mutation-positive was found in a medical checkup to have a submucosal tumor (SMT). Endoscopy showed the 9 cm SMT to be located in the lesser curvature of the posterior pyloric wall. Immunohistochemical staining of biopsy specimens were all negative for c-kit, CD34, alpha-SMA and S100. Suspecting the SMT to be gastric GIST, we conducted distal gastrectomy. Abdominal computed tomography and diffusion-weighted magnetic resonance imaging indicated that the tumor grew both inward and outward, but no liver or peritoneal metastasis was seen. Pathologically, spindle and epithelial-like cells had formed irregularly. Only CD34 immunohistochemical stein was positive, while c-kit, alpha-SMA and S100 were negative. No KIT gene mutation was detected, but PDGFR-alpha mutation D842V was identified in exon 18. The size was 85 mm and the mitotic index was two cells per 50 high-power fields. This classified the GIST into an immediate risk group. Surgery was curative, and the PDGFR-alpha exon 18 D842V mutation was imatinib-resistant, so the man was followed up without adjuvant therapy. For the postoperative treatment strategy, gene search of GIST was useful.

Key words
GIST, stomach, PDGFRA

Reprint requests
Hiroshi Nimura Department of Surgery, The Jikei University School of Medicine
3-25-8 Nishi-shinbashi, Minato-ku, 105-8461 JAPAN

Accepted
May 27, 2009

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