The Retroperitoneal Gastrointestinal Stromal Tumor, Simulating a Cystic Pancreatic Neoplasia. A Case Report.

Introduction: Gastrointestinal stromal tumors (GISTs) are rare mesenchymal tumors that can arise anywhere within the gastrointestinal tract. Approximately 70 % are in the Stomach, representing 1 – 3 % of all gastrointestinal malign neoplasms. GISTs originate from the Cajal interstitial cells or their stem cell precursors within the myenteric plexus of the muscularis propria.  Histologically, GIST presents three different architectural patterns: a. composed of epitheloid cells embedded in a thin reticular stroma; b. by spindle cells with a fascicular or storiform arrangement immersed in a thin reticular stroma focally myxoid, and c. the mixed forme. This study describes a 72-year-old man who, in the computed tomography, presented a gross appearance as pancreatic cystic neoplasia. Clinicians should be aware that this condition might be mistaken for a primary pancreatic malignancy. The diagnostic Workup includes endoscopy with ultrasonography, cross-sectional imaging studies, and histopathological examination.  Conclusions: The reported case illustrates that the retroperitoneum might be the place of initial presentation of a cystic gastric GIST and that only an accurate pathological evaluation can establish the diagnosis and origin. Clinicians must know this condition might be mistaken for a primary pancreatic malignancy. Early surgical resection is the gold standard of treatment for primary GIST.