Gastrointestinal Stromal Tumor with Dedifferentiation to Pleomorphic Sarcoma during Neoadjuvant Chemotherapy with Imatinib Mesylate: A Case Report

Aoki Ryota, Gomyo Yoshihito, Ikeno Tatsuo, Akita Noriyuki, Park Yonghan, Miyamoto Hideo, Makino Mutsuki, Kawaguchi Kenji

doi:10.5833/jjgs.2021.0162

<p>A 75-year-old man was referred to our hospital after a CT scan revealed a 20-cm mass in his stomach. Endoscopic examination revealed a gastric submucosal tumor. Pathological examination of biopsy tissue showed spindle-shaped cells that were CD117-positive, CD34-positive, S100-negative, and desmin-negative. The patient was diagnosed with a gastrointestinal stromal tumor (GIST). Neoadjuvant chemotherapy with imatinib mesylate was initiated because CT showed that the tumor had invaded the liver and diaphragm. The tumor shrunk to 11 cm after 7 months, but had not shrunk further at 11 months, at which time we decided to perform resection. However, because the tumor was no longer invading the liver and diaphragm, partial gastrectomy and splenectomy were performed. Pathological examination of the resected specimen revealed highly pleomorphic mesenchymal atypical cells that differed from those in the preoperative biopsy tissue, and CD117 and CD34 were both negative. The tumor was diagnosed as pleomorphic sarcoma dedifferentiated from GIST. We report this case as a rare example of dedifferentiated GIST and we provide a literature review.</p>

Gastrointestinal Stromal Tumor with Dedifferentiation to Pleomorphic Sarcoma during Neoadjuvant Chemotherapy with Imatinib Mesylate: A Case Report

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