A Case of the Unveiling of Pulmonary Pseudoaneurysm Masquerading as a Lung Mass

Pulmonary artery pseudoaneurysm (PAP) is an abnormal dilatation of the pulmonary vessels. They can mimic the appearance of lung nodules on chest X-rays and noncontrast CT imaging of the chest. We present a case of PAP masquerading as a lung mass for five years before presenting as a pulmonary hematoma. Our patient was an elderly male who presented to the emergency department with dizziness and weakness. He had been on regular follow-ups with annual noncontrast CT scans for a stable lung mass for the past five years. A contrast-enhanced chest CT scan on presentation showed a right lower lobe pseudoaneurysm ruptured into the pleural space with hemothorax, which was confirmed on subsequent chest CTA. The patient underwent an emergent right lower lobe resection and recovered uneventfully. Differentiating a PAP from a lung nodule is challenging and is often missed even by radiologists. A nodule or mass along the pulmonary arterial tree should raise suspicion and trigger further contrast-enhanced imaging, especially angiography, to confirm the diagnosis.