Non-Thrombotic Pulmonary Embolism

Tumor Embolism Tumor embolism is not rare at autopsy (3–26%), particularly in solid tumors that tend to invade systemic veins (hepatocellular, renal cell, breast, chondrosarcoma or lung carcinoma) (Figure 1). The condition remains however underdiagnosed in clinical routine, even on computed tomography (CT) or magnetic resonance (MR). Most tumor emboli are microscopic and involve peripheral pulmonary arteries (PAs) and arterioles, except the right atrial myxoma, renal cell carcinoma or chondrosarcoma that may embolize to the central and segmental PAs. Symptoms include progressive dyspnea and subacute pulmonary hypertension or a more acute presentation that may simulate pulmonary embolism (PE). On CT, they may present as multifocal dilations or beading of PAs, sometimes showing a tree-in-bud pattern (Figure 2). Areas of mosaic perfusion, pulmonary infarction or even a pattern of pseudo-consolidation of lung parenchyma have been reported. Findings that should allow differentiation from cruoric PE include absence of risk factor for PE, absence of regression under anticoagulation, lobulated or heterogeneous components, enhancement after CM administration and transmural extension. They should also be differentiated from filling-in of dilated bronchial structures, i.e., mucous plugging in bronchiectasis or endobronchial growth of tumor.