A Case of Imatinib Mesylate-Resistant Gastrointestinal Stromal Tumor Arisen in the Mesentery Having Mutation at Exon 9 of the c-kit Gene

Takayuki Suto, Tamotsu Sugai*, Noriyuki Uesugi*, Wataru Habano*, Shin-ichi Nakamura* and Kazuyoshi Saito**

Department of Surgery, Morioka Municipal Hospital
Division of Pathology, Central Clinical Laboratory, School of Medicine, Iwate Medical University*
Department of Surgery I, School of Medicine, Iwate Medical University**

We report an imatinib mesylate-resistant gastrointestinal stromal tumor (GIST) arising in the mesentery analyzed by c-kit mutation. A 58-year-old man examined for abdominal distension on July 27, 2002, was hospitalized on September 6, 2002, for a huge tumor in the hypogastric region detected by CT. The patient underwent resection of the mesenterial tumor, right hemicolectomy, and enterectomy on September 12, 2002. Histopathologically, the tumor was composed of a fascicular proliferation of spindle-shaped cells with marked mitosis. Immunohistochemically, tumor cells were positive for c-kit but negative for CD34, actin, and s-100. The tumor was diagnosed as malignant GIST arising in the mesentery. Treatment with imatinib mesylate at a dose of 400 mg/day was initiated on October 27, 2002. CT showed multiple tumors on April 4, 2003. The patient underwent tumor resection again on April 23, 2003. Treatment with imatinib mesylate at a dose of 400 mg/day was resumed on May 16, 2003, but on December 12, 2003, CT showed multiple tumors. The patient underwent further tumor resection on December 24, 2003. We suspected this case was imatinib mesylate-resistant GIST and analyzed c-kit mutation by using direct sequencing. A 6 base-pair insertion (GCC TAT) was found at c-kit exon 9 between codons 503 and 504. This case suggests that analysis of the c-kit mutation may be usefull as a prognostic factor and the evaluation of the effect of imatinib mesylate.

Key words
imatinib mesylate, gastrointestinal stromal tumor, c-kit

Reprint requests
Takayuki Suto Department of Surgery, Morioka Municipal Hospital
15-1 Koyashiki, Motomiya, Morioka, 020-0866 JAPAN

Accepted
September 22, 2004

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