A 55-year-old woman was diagnosed with primary GIST of the stomach….Based on the gene analysis and the later multiplex gene panel testing, we confirmed that this tumor had a PDGFRA D842V mutation….The patients were assigned to the PIMI group. She received oral PIMI 160 mg/day under fasting conditions for 5 consecutive days, followed by a 2-day rest in a 21-day cycle (Fig. 3)....For the first 8 months after the initiation of PIMI administration, the tumor size remained stable, and the effect of PIMI was slight. However, at the ninth month of administration, the patient achieved a partial response (Fig. 3). The highest reduction rate was 32.7%....We encountered a case of PDGFRA D842V mutant GIST with a long-term response to PIMI.