Epithelioid gastrointestinal stromal tumor with PDGFRA activating mutation and immunoreactivity.

Eunhee S Yi, Curtis R Strong, Zhe Piao, Manuel Perucho, Noel Weidner

Department of Pathology, University of California San Diego, School of Medicine, San Diego, CA 92103-8720, USA. jeyi@ucsd.edu

Applied immunohistochemistry & molecular morphology : AIMM / official publication of the Society for Applied Immunohistochemistry 2005 Jun

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The authors report a unique case of an intra-abdominal, epithelioid mesenchymal tumor that had an activating mutation of PDGFRA and a strong PDGFRA immunoreactivity but lacked both c-kit mutation and c-kit protein (CD117) expression. IHC study showed that the tumor cells were diffusely and strongly positive for PDGFRA, vimentin, CD34, and Bcl-2 but completely negative for CD117 as well as for muscle, epithelial, endothelial, endocrine, mesothelial, neural, and melanocytic cell markers. Molecular study revealed a mutation at the juxtamembrane domain of exon 12 in PDGFRA gene with GTC to GAC transition at codon 561 (V561D), as shown in the previous mutational studies on gastrointestinal stromal tumor (GIST). This case likely represents an example of GIST with PDGFRA activating mutation and PDGFRA immunoreactivity without CD117 positivity, which has not been documented in the literature. STI 571 (imatinib mesylate [Gleevec]) might be an effective therapy in this case, since Gleevec targets both PDGFRA and c-kit oncoproteins.

Citation

Eunhee S Yi, Curtis R Strong, Zhe Piao, Manuel Perucho, Noel Weidner. Epithelioid gastrointestinal stromal tumor with PDGFRA activating mutation and immunoreactivity. Applied immunohistochemistry & molecular morphology : AIMM / official publication of the Society for Applied Immunohistochemistry. 2005 Jun;13(2):157-61