Abstract
BACKGROUND: Collision tumors involving the small intestine, specifically the combination of a hamartomatous tumor and a lipoma, are extremely rare. To our knowledge, no previous case report has described a collision tumor composed of two benign tumors of different origins in the small intestine. CASE SUMMARY: Here, we present the case of an 82-year-old woman who presented with hemorrhagic shock and was found to have a mass measuring approximately 50 mm × 32 mm × 30 mm in the terminal ileum. Based on computed tomography scan findings, the mass was initially suspected to be a lipoma. A subsequent colonoscopy revealed a pedunculated submucosal elevation consisting of two distinct parts with a visible demarcation line. A biopsy of the upper portion suggested a juvenile polyp (JP). Owing to the patient's advanced age, multiple comorbidities, and poor surgical tolerance, a modified endoscopic submucosal dissection was performed. Histopathological examination of the excised mucosal mass revealed a lipoma at the base and a JP at the top, demonstrating evidence of rupture and associated bleeding. The patient's overall health remained satisfactory, with no recurrence of hematochezia during the six-month follow-up period. CONCLUSION: This case report provides new evidence for the understanding of gastrointestinal collision tumors, emphasizing their diverse clinical presentations and histopathological characteristics. It also offers diagnostic and therapeutic insights as well as an approach for managing benign collision tumors.