Recurrent retroperitoneal inflammatory myofibroblastic tumor in an elderly patient: Diagnostic pitfalls and implications for long-term follow-up

• Retroperitoneal inflammatory myofibroblastic tumor in an elderly patient is exceptionally rare and challenging. • Multimodal imaging revealed a large hypervascular mass mimicking other retroperitoneal soft-tissue tumors. • Histology showed ALK-negative IMT with very low Ki-67 (<1%), yet local recurrence occurred. • Even after complete resection, long-term structured imaging follow-up is essential to detect IMT recurrence.