Ex vivo evaluation of a prototype submucosal biopsy forceps for the diagnosis of gastric gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) account for approximately 2% of gastric cancers and can be challenging to diagnose due to the difficulty sampling tissue from these lesions. Current biopsy methods are inadequate for determining the mitotic index, a major prognostic factor of these tumors. We sought to evaluate the ability of a prototype submucosal biopsy forceps to make a histologic diagnosis and mitotic index determination in cases of resected gastric GISTs. After obtaining informed consent and surgical resection of three gastric GISTs, an investigational submucosal biopsy forceps and sheath was passed under direct visualization into the central portion of the tumors (in the ex vivo setting) and biopsies were obtained. The tumor was then processed for standard histology. A gastrointestinal pathologist, blinded to the mitotic index of the full specimen, evaluated the research biopsies. The results from the submucosal forceps biopsies were then compared with the standard histology results. In all 3 cases, the submucosal forceps biopsies confirmed the diagnosis of a GIST. In two out of three cases, the submucosal forceps biopsies accurately classified the risk for progressive disease (based on the mitotic index) when compared to standard histology. In one case, the research biopsy mitotic index would have resulted in an underestimation of tumor risk (biopsies categorized the lesion as “very low” rather than “moderate” risk).