An observational study of gastrointestinal stromal tumors by histopathology and immunohistochemistry

Introduction: Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the gastrointestinal tract and their diagnosis is mainly based on histopathology and immunohistochemical study with CD117 marker. However, there are many GIST tumors that are CD117 negative and for such cases come the role of other IHC markers. The study aimed to observe the various histological features and demographic profiles of GISTs and the role of various immunohistochemical markers in the confirmation of diagnosis. Methodology: A hospital-based observational study was conducted on 40 tumor resection materials diagnosed as GIST from April 2017 to February 2023 at tertiary care center K.E.M. Hospital, Pune. All the cases underwent histopathological examination with standard procedure of tissue processing, staining and IHC with CD117. Those cases who were morphologically designated as GIST on HPE were evaluated with a panel of IHC markers like C-KIT, CD34, SMA, desmin, S-100 and vimentin. Results: 35 out of 40 cases (87.5%) were found to be positive for CD117 while IHC markers like CD34, SMA, desmin, S-100 and vimentin were found to be positive in 60%, 20%, 5%, 2.5% and 80% cases respectively. Also, we found significant relationship between histopathological groups different progressive disease risk groups with necrosis, cytologic atypia, cellularity and mucosal invasion (p-value<0.05) Conclusion: In a nutshell, a GIST diagnosis should not be precluded on the basis of morphology only. Use of immunohistochemistry is vital to rule out other mesenchymal tumors and confirmation of GIST. Keywords: GIST; gastrointestinal stromal tumors; IHC; CD 117; histopathology; c-KIT