Pulmonary tumor embolism
Pulmonary tumor embolism refers to a specific type of pulmonary embolism where the embolic constituents comprise of tumor components/particles or tumor thrombus. It can either be microscopic or macroscopic.
Pathology
Microscopic tumor embolism
Thought to occur from two distinct pathophysiological processes. The first is primarily related to tumor foci and is a unique form of tumoral accumulation because embolic foci usually do not invade the arterial wall. The second process is due to thrombotic microangiopathy of pulmonary tumors (pulmonary tumor thrombotic microangiopathy).
Some of the more typical primaries include
- hepatocellular carcinoma
- choriocarcinoma
- breast carcinoma
- gastric carcinoma
- primary lung carcinoma
- pancreatic carcinoma
- prostate carcinoma
Macroscopic tumor embolism
Some of the more typical primaries include
It can also be seen in
Radiographic features
CT (angiography)
Appearances can be variable and sometimes non-specific.
Microscopic pulmonary tumor embolism has may give a tree-in-bud pattern on CT in some cases.
In macroscopic emboli, both bland and tumor emboli can appear as focal hypo-attenuating pulmonary arterial filling defects on CT pulmonary angiography. Further differentiation can often be difficult unless a specific substance such as fat or calcific content is seen in the appropriate clinical context (e.g. angiomyolipoma and osteosarcoma).
Multifocal dilatation and beading of the peripheral subsegmental arteries and peripheral wedge-shaped areas of attenuation due to infarction/vascular occlusion may be present .
On some occasions, tumoral enhancement of an intra-arterial filling defect may be seen .
A lack of sufficient size reduction in emboli despite adequate thrombolytic therapy on follow up scans could raise suspicion in some cases.
