Pulmonary Embolism or a Fatal Mimic? Wall-Eclipsing Sign and Metastatic Tissue Diagnosis in Pulmonary Artery Intimal Sarcoma: A Case Report

Background Pulmonary artery intimal sarcoma is a rare, aggressive malignancy that may mimic chronic pulmonary infection and chronic thromboembolic disease. This case highlights the need to reconsider a thromboembolic diagnosis when pulmonary arterial obstruction persists despite anticoagulation and is associated with the wall-eclipsing sign and progressive right ventricular failure. Case Summary A 50-year-old woman presented with 3 months of intermittent haemoptysis and progressive dyspnoea. Initial evaluation suggested chronic infectious lung disease; however, transthoracic echocardiography identified a mass involving the main pulmonary artery. Computed tomography pulmonary angiography was initially interpreted as chronic pulmonary thromboembolism, and anticoagulation was initiated. Shortly thereafter, life-threatening haemoptysis required high-flow nasal oxygen therapy, transfusion of four units of packed red blood cells, and vasopressor support. Follow-up imaging showed persistent pulmonary arterial obstruction with progressive right ventricular failure. Repeat computed tomography pulmonary angiography demonstrated an infiltrative pulmonary artery mass with intrinsic enhancement, left atrial extension, and the wall-eclipsing sign. Breast nodules and axillary lymphadenopathy prompted biopsy of an accessible breast lesion, which revealed a high-grade spindle-cell neoplasm with CD31 and ERG expression, supporting angiosarcomatous differentiation, together with nuclear MDM2 immunoreactivity. Fluorescence in situ hybridisation demonstrated MDM2 gene amplification in the breast biopsy, supporting the integrated diagnosis of pulmonary artery intimal sarcoma with angiosarcomatous differentiation and breast metastasis. Discussion This case highlights the need to reconsider chronic thromboembolic disease when pulmonary arterial obstruction persists despite anticoagulation, particularly in the presence of the wall-eclipsing sign. Metastatic tissue sampling may establish the diagnosis while avoiding high-risk intravascular biopsy.