Background: With the advent of immunohistochemical analysis, the term "gastrointestinal stromal tumor" (GIST) was proposed to designate the largest category of primary nonepithelial neoplasms. EUS-guided fine needle aspiration (EUS-FNA) is useful for diagnosis of GISTs. The aim of this study was to evaluate the phenotyping of GISTs and diagnosis of malignant GISTs by using EUS-FNA with immunohistochemical analysis. Methods: A diagnosis of GIST was made in 23 patients by using EUS-FNA with immunohistochemical analysis. The accuracy of EUS-FNA diagnosis compared with the EUS imaging alone was analyzed. Additionally, immunophenotyping of specimens obtained by EUS-FNA and surgical resection specimens was compared. Factors that were diagnostic for malignant GISTs were also analyzed. Results: The overall accuracy for the diagnosis of malignant GIST was 78% (18/23) by EUS imaging alone and 91% (21/23) by histopathologic evaluation (H&E staining) of specimens obtained by EUS-FNA. In 21 of 23 cases (91%) the immunohistochemical expressions of c-kit, CD34, muscle actin, and S-100 coincided for the FNA and surgical specimens. The presence of mitotic cells (p = 0.011) and the Ki-67 labeling index (p < 0.0001) with respect to the FNA specimens were significant predictive factors for malignant GIST. For the diagnosis of malignant GIST, the accuracy, sensitivity, and specificity of EUS-FNA with the addition of Ki-67 immunohistochemical staining were 100%. Conclusions: EUS-FNA with immunohistochemical analysis is useful in the preoperative diagnosis of GIST. It provides abundant information on immunohistochemical subtyping and on the capacity of the tumor for cellular progression.
All Science Journal Classification (ASJC) codes