Abstract
Gastrointestinal stromal tumors (GIST) are tumors of mesenchymal origin, accounting for less than 1% of the primary neoplasms of the digestive tract, which can affect any segment of the gastrointestinal tract. However, they can also occur in other locations outside the gastrointestinal tract. In such situations, these are known as extragastrointestinal stromal tumors (eGIST). We present a 58-year-old male, who attended the emergency department due to asthenia, anorexia, heartburn, abdominal pain, and distension, who was ultimately diagnosed with an eGIST in the peritoneum. The immunohistochemistry pattern of the tumor sample obtained favored this diagnosis, especially demonstrated by the positivity for discovered on GIST protein 1 (DOG1) and negativity of smooth muscle markers. Due to the rarity of extragastrointestinal tumors and the even greater rarity of those originating in the peritoneum, the authors consider this a pertinent clinical case to be published due to its originality.