Molecular Profile of Gastrointestinal Stromal Tumors in Sixty-Eight Patients from a Single Swiss Institution.

Introduction:Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. It has distinct molecular features and primarily affects theKITandPDGFRAgenes.Objective:We wanted to assess the molecular profile of 68 GIST patients who were sequenced consecutively between 2014 and 2019 at our institute of pathology.Methods:Our cohort comprised 60 primary and 8 metastatic GIST patients; 43 and 57% of the cases, respectively, were analyzed by Sanger sequencing or next-generation sequencing (NGS).Results:Of the 60 primary GIST patients, 47 (78%) showed aKITmutation; 2 cases showed a doubleKITmutation, and 1 of these was a therapy-naive GIST. Nine (15%) patients harbored aPDGFRAmutation, 2 (3%) had aBRAFmutation, 1 (2%) had aPIK3CAmutation, and 1 (2%) did not show any mutation. OneBRAFand thePIK3CAmutation have not been described in GIST before. All metastatic GIST harbored exclusivelyKITmutations.Conclusion:A retrospective analysis of GIST sequenced at our institute revealed incidences ofKITandPDGFRAmutations comparable to those in other cohorts from Europe. Interestingly, we found 2 previously undescribed mutations in theBRAFandPIK3CAgenes as well as 1 treatment-naive case with a doubleKITmutation in exon 11.