Study of Histomorphological Spectrum of Mesenchymal Tumors of GIT at Tertiary Care Centre

Abstract

Introduction: Mesenchymal neoplasms of gastrointestinal tract are a group of rare tumors with overlapping histological features. There is significant morphologic overlap among diagnostic entities on the differential of mesenchymal lesions. So, use of a panel of immunohistochemical antibodies is necessary for accurate characterization of mesenchymal lesions of gastrointestinal system. Aim: The study was conducted in a tertiary care hospital in western India between January, 2019 to June 2020 to study the histomorphological spectrum and utility of IHC in the final diagnosis of mesenchymal tumor of GIT. Material & Methods: The cases were selected on the basis of inclusion & exclusion criteria defined and thereafter a panel of IHC antibodies was applied to diagnose mesenchymal tumors of gastrointestinal tract. Results: The study included 92 cases with a clinical and provisional morphologic diagnosis of mesenchymal tumors of GIT, mesentery and omentum. 25.00% cases of MT of GIT and were diagnosed on morphology alone. While, 75.00% required IHC for final diagnosis. Tumors with spindle cell morphology 61.95%, epithelioid cell morphology 5.80%, with mixed (spindle+epithelioid) cell morphology 10.14% and pleomorphic cell morphology 1.45%. Using” WHO 2013 of soft tissue tumors” MT of GIT were classified according to clinical behavior in to Benign tumors in 44.57% cases, lipoma being the commonest tumour diagnosed 34.15% cases. Intermediate tumors in 8.70% cases, all cases 100% being fibromatosis. Malignant tumors in 46.74% cases. Using “WHO 2019 of MT of Digestive System”, tumors were classified based on cell type. The commonest phenotype was “GIST” with 42.39% cases, followed by the second common phenotype “Adipose and Myofibroblastic tumor” with 33.69% cases, “Smooth and Skeletal Muscle tumors” with 9.78% cases. “Neural Tumors” with 7.63% cases, “Vascular and Perivascular” with 5.43% cases. Conclusion: GIST are the commonest MT of GIT. The availability of targeted chemotherapy warrants confirmation and ruling out GIST amongst all MT on priority basis. IHC panel should be applied in stepwise manner over “morphologically suspicious” cases Mesenchymal Tumors of GIT to diagnose and rule out GIST with first panel being CD117 and DOG1. These optimize the use of antibodies and make it cost effective. Keywords: Mesenchymal tumors, GIST, CD 117, DOG 1 antibody