A CT chest shows a central hypodense filling defect surrounded by a rim of contrast within the pulmonary artery. This 'polo mint' or 'doughnut' sign is seen in which condition?

• A Central pulmonary artery tumour embolus
• B Chronic pulmonary thromboembolism with recanalization ✓
• C Pulmonary artery sarcoma
• D Mucous plug in airway

Explanation

Chronic pulmonary thromboembolism with partial recanalization shows eccentric or central filling defects that may exhibit the polo mint sign (contrast surrounds a partially recanalized thrombus). This is distinct from acute PE which shows a saddle embolus or abrupt cutoff. Over time, chronic thrombus organises and partially recanalizes, leaving an eccentric, web-like, or partially obstructing filling defect. Pulmonary artery sarcoma is a rare mimic appearing as a filling defect extending into proximal arteries. Tumour emboli tend to be multiple and peripheral.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.