Abstract
A 66-year-old male was diagnosed with a gastric gastrointestinal stromal tumor (GIST) accompanied by peritoneal dissemination and treated with 400mg/day of imatinib. On month after the initiation of administration, both the primary gastric lesion and intraperitoneal mass decreased in size, showing partial remission. Seven weeks after the initiation of administration, drug-induced interstitial pneumonia developed, but improved after steroid pulse therapy. Extensive mediastinal emphysema developed 6 days after the initiation of steroid therapy, but improved after conservative treatment. Subsequently, he died of bacterial pneumonia. During imatinib administration, caution is necessary regarding the possible development of interstitial pneumonia.
