Aortic malignancy masquerading as infrarenal aortitis: A diagnostic challenge.

Primary retroperitoneal aortic sarcoma is an exceptionally rare malignancy and may closely mimic inflammatory or infectious aortitis on clinical assessment and imaging. An 89-year-old man presented with abdominal pain, weight loss, and periaortic inflammatory change on computed tomography, raising concern for aortitis with possible impending rupture. Urgent endovascular aortic repair was performed. Despite antimicrobial and immunosuppressive therapy, symptoms and radiographic findings progressed. Subsequent computed tomography-guided biopsy demonstrated a high-grade retroperitoneal aortic sarcoma. The presence of the stent graft influenced perceived procedural safety and allowed tissue diagnosis that had initially been deferred. This case highlights the diagnostic challenge posed by malignant aortic disease presenting as presumed aortitis and underscores the importance of maintaining diagnostic vigilance in atypical cases.