A Novel Fusion between CDC42BPB and ALK Exon 20 in a Patient with Wild Type Gastrointestinal Stromal Tumor: a case report

Abstract

Background Gastrointestinal stromal tumors (GISTs) are the most common type of mesenchymal tumor in gastrointestinal tract (GI), with striking features of morphology and immunohistochemistry. Pathogenic activating mutations of the proto-Oncogene Kit are detected in 80–85% GISTs, while 5–7% of cases harbor activating mutations of platelet derived growth factor receptor alpha (PDGFRA). There are still some rare mutation types, including succinate dehydrogenase (SDH)-x, BRAF, RAS and NF1 mutations, or ETV6-NTRK3 fusion. Herein, we reported the first case of GIST with ALK gene rearrangement and ALK (D5F3) overexpression. Case presentation In this study, we described a 33-year-old female patient who appeared a massive space occupying lesion (with the maximum diameter of 22 cm) in the stomach and was eventually diagnosed as Kit and PDGFRA wide type GIST. We unexpectedly found that GIST of this patient showed ALK (D5F3) overexpression and harbored a novel fusion CDC42BPB exon 24-ALK in exon 20. Conclusion This is the first case of GIST with both ALK rearrangement (CDC42BPB exon 24-ALK in exon 20) and ALK (D5F3) overexpression. This rare phenomenon might suggest that ALK (D5F3) immunohistochemistry could be a screening tool for ALK-rearranged GIST. In addition, ALK inhibitors could be a potential therapeutic target for patients (with ALK rearrangement), which should be confirmed further.