| Summary: | Accumulating evidence reveals the heterogeneous features of gastrointestinal stromal tumors (GISTs), primarily distinguished by their various molecular triggers defining well characterized subgroups. The identification of the pathogenetic group a given GIST belongs to, in combination with the currently adopted GIST prognosticators, is pivotal for the correct management of GIST patients. Epidemiological, anatomical and morphological features are more or less strictly associated with the various possible GIST molecular pathogenesis; therefore, they can concur to addressing molecular analysis or even influence the identification of GIST subsets by themselves. This is particularly true in a cost/benefit perspective aimed at cutting the expenses of pathology labs. Under these circumstances, a correct classical pathological analysis still appears a fundamental step to achieve an optimal GIST characterization.We herein report a gastric epithelioid PDGFRA-mutant GIST displaying the multinodular/plexiform architecture distinctive of succinate dehydrogenase (SDH)-deficient GISTs. Immunohistochemistry and molecular analysis led to the correct tumor characterization. The reported case constitutes a valuable contribution to GIST pathology in that it demonstrates that multinodular/plexiform architecture is not restricted to SDH-deficient GISTs, but can be found also in PDGFRA-mutant ones; this is an event to be aware of, given the predilection for gastric location and epithelioid morphology shared by these two GIST subgroups, only the latter of which includes imatinib-sensitive cases. Keywords: Gastrointestinal stromal tumor, Platelet-derived growth factor receptor alpha, Multinodular architecture, Plexiform architecture, Succinate dehydrogenase
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