Perirectal Extragastrointestinal Stromal Tumor: An Unusual Presentation.

Gastrointestinal stromal tumors (GISTs), even though rare, remain the most common mesenchymal tumors of the gastrointestinal (GI) tract. When GISTs occur outside of the GI tract, they are termed extragastrointestinal stromal tumors (EGISTs). Most GISTs arise from the stomach (50-70%) and small intestine (20-30%). A smaller percentage of these tumors also occurs in the large intestine (5%) and esophagus (2-5%). EGISTs have histopathological and molecular characteristics that are similar to GISTs. However, the precise incidence and tumor behavior of EGISTs are not fully understood. EGISTs have no specific symptoms or radiologic features, and in most cases, the presenting complaint is abdominal pain or discomfort. Yet, they tend to be more aggressive and have a worse prognosis than GISTs. Morphologic diagnosis based on microscopic examination of histological sections is the standard diagnostic procedure for GIST/EGIST. In this patient-centered study, we present a case of EGIST that originated in the anterior perirectal space, an extremely rare location; we also describe the endoscopic approach that was used to biopsy the tumor.