Context Gastrointestinalstromal tumors are CD117 (C-Kit) positive mesenchymal neoplasms considered tooriginate from the interstitial cells of Cajal. Gastrointestinal stromal tumorshave been described outside the gastrointestinal tract in sites, such as themesentery, omentum and retroperitoneum; however, pancreatic extra-gastrointestinalstromal tumors are extremely rare and there have only been seven previousreports in the literature. Case report We describe a 38-year-old manwith a malignant pancreatic gastrointestinal stromal tumor. The tumor waslocated in the head of pancreas, measured 6.5x5.0 cm and was wellcircumscribed. On histology, it showed a mixed spindle and epithelioid cellmorphology with the presence of sheets and short intersecting fascicles oftumor cells. There was a mitotic count of 12-15 mitoses per 50 high-powerfields. The differential diagnosis included a pancreatic smooth muscle tumorand a neuroendocrine tumor. Immunohistochemistry revealed diffuse cytoplasmicpositivity for CD117 and vimentin. Tumor cells were negative for CD34, S100,desmin, smooth muscle actin (SMA), cytokeratin, neuron specific enolase,chromogranin and synaptophysin. The patient developed isolated liver metastasistwo years after the resection of the primary tumor. The resected metastasisshowed a similar tumor. The patient was treated with imatinib mesylate and thepost-operative course two years after resection of the liver metastasis hasbeen uneventful. Conclusion We report a rare case of pancreatic gastrointestinalstromal tumor presenting as a solid neoplasm and review the cases previouslydescribed in the literature.
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