Which imaging study would be ordered to evaluate a possible Pancoast tumor causing Horner syndrome?

• A. Chest CT
• B. Brain MRI
• C. Abdominal ultrasound
• D. Eye ultrasound

Answer: (A)

When Horner syndrome raises suspicion for a Pancoast tumor, the imaging study of choice is a chest CT with contrast. This test directly visualizes the lung apex where Pancoast tumors arise and provides detailed information about the tumor’s size, exact location, and whether it invades nearby structures such as the chest wall, ribs, vertebrae, or the sympathetic chain. That information is essential for confirming the diagnosis, staging the disease, and planning treatment. Brain MRI isn’t the first step here, because Horner’s in this context is most often due to a chest apex lesion rather than intracranial pathology. Abdominal ultrasound and eye ultrasound don’t address the suspected chest-based tumor and aren’t helpful for evaluating apical lung disease.