[A Case of Epithelioid-Type Small Intestinal Gastrointestinal Stromal Tumor with Positive PDGFRA Discovered Because of Small Intestinal Intussusception].

Adult intussusception is a rare condition, accounting for approximately 5% of all intussusception cases, and is often caused by organic lesions, such as tumors. We report a rare case of a small intestinal gastrointestinal stromal tumor(GIST)presenting with intussusception. The patient was an older adult woman in her 80s who presented with abdominal pain and loss of appetite. Abdominal contrast-enhanced CT revealed an intussusception with a 30-mm mass as the lead point, and emergency surgery was performed to remove the mass. Segmental resection of the small intestine was performed, and histopathological examination revealed a submucosal epithelioid tumor. Immunohistochemical analysis revealed that both KIT and DOG1 were negative, making diagnosis difficult. However, PDGFRA positivity was confirmed by additional testing, leading to a final diagnosis of GIST. Small intestinal GISTs are relatively uncommon, and epithelioid-type GISTs that are KIT-negative and DOG1-negative are extremely rare. This case highlights the importance of considering atypical GISTs in the differential diagnosis of small bowel tumors with unusual immunohistochemical features.