Abstract
RATIONALE: Follicular dendritic cell sarcoma (FDCS) is a rare mesenchymal tumor that typically develops in lymph nodes; it is clinically uncommon and has only occasionally been documented in cases of soft tissue, liver and spleen, and retroperitoneum; it is also extremely uncommon to develop in the stomach. PATIENT CONCERNS: A 64-year-old woman who discovered a lump in her left upper abdomen 6 months prior and was taken to the hospital due to excruciating abdominal pain. DIAGNOSIS: An abdominal computed tomography scan showed a soft tissue mass around the cardia. The immunohistochemical and postoperative histopathology results were compatible with FDCS. INTERVENTIONS: The patient underwent "radical total gastrectomy and esophagojejunostomy" (Roux-Y anastomosis). OUTCOMES: The patient recovered well 2 months after surgery. LESSONS: We report a case of FDCS occurring in the stomach and abdominal cavity, which was unique in terms of clinical location, clinical presentation, and imaging signs. This case report aims to enhance clinicians' understanding and diagnosis of FDCS in the stomach and abdominal cavity and reduce the rate of clinical misdiagnosis.