Primary esophageal gastrointestinal stromal tumor with PDGFRA mutation

Gastrointestinal stromal tumors (GISTs) of the esophagus are a rare entity. Diagnosis of GIST is currently based on immunohistochemical staining of c-KIT or CD34. However, some tumors have clinicopathologic features of GIST but do not express c-KIT or CD34. A few GISTs contain mutations within a receptor tyrosine kinase protein, platelet-derived growth factor receptor alpha (PDGFRA). We herein report a case of esophageal GIST that was KIT negative and had a PDGFRA mutation. A 75-year-old male who had a giant submucosal tumor in the lower part of the thoracic esophagus underwent surgical resection. Immunohistochemical staining of the tumor revealed that it was uniformly negative for KIT, but partially positive for CD34, and negative for S-100 protein and smooth muscle actin (SMA), which led to the final diagnosis of GIST. PDGFRA genetic testing revealed a mutation in exon 12. The mitotic index was over 5/50 high-power fields, and necrotic changes were noted. Adjuvant chemotherapy using imatinib mesylate was administered. The patient has been disease free for 2 years. To the best of our knowledge, this is the only reported case of esophageal GIST that was KIT negative and had a PDGFRA mutation. In cases of digestive submucosal tumor that are difficult to diagnose because of c-KIT or CD34 negativity despite being suspicious for GIST, PDGFRA genetic testing may help for diagnosis of this minority type of GIST.