Gastrointestinal stromal tumor with a platelet-derived growth factor receptor-alpha mutation
A 44-year-old man visited a local hospital, complaining of abdominal pain. The patient presented with muscular guarding in the upper abdomen and moderate anemia (hemoglobin, 6.7 g/dL). Computed tomography revealed a 9.0-cm tumor adjacent to the stomach and massive ascites (Panel A). The patient was diagnosed with hemoperitoneum caused by tumor rupture, and underwent laparotomy. Pathological examination revealed that the excised tumor was microscopically composed of cytoplasm-rich polygonal cells that were immunohistochemically positive for CD34 but negative for KIT (Panel B). Gene analyses revealed that the tumor had a deletion mutation in exon 18 (del 842-845) of platelet-derived growth factor receptor alpha (PDGFRA). Based on this finding, confirmative diagnosis of gastrointestinal stromal tumor (GIST) of the stomach was made. Despite tumor rupture, which is a significant risk factor for recurrence, the patient was postoperatively followed up without adjuvant treatment with imatinib because the PDGFRA-mutated GIST was reportedly resistant to the tyrosine kinase inhibitor (1). Eight years after the surgery, the patient is alive with no evidence of disease recurrence.