The presence of widespread tumor microemboli within small pulmonary arteries (tumor thrombotic microangiopathy) can cause pulmonary arterial hypertension. The diagnosis may be missed since it is relatively rare.


Tumors that can send microemboli within small pulmonary arteries:

(1) breast cancer

(2) lung adenocarcinoma

(3) hepatocellular carcinoma

(4) gallbladder adenocarcinoma

(5) gastric adenocarcioma

(6) choriocarcinoma

(7) chondrosarcoma


Diagnostic features:

(1) Usually the patient has a history of cancer.

(2) The patient presents with signs and symptoms of pulmonary arterial hypertension.

(3) Routine chest imaging studies are normal or almost normal.

(4) The tumor microemboli are usually not seen in bronchial biopsies.


Certain imaging studies (perfusion radionuclide lung scan, PET scan) can show the tumor but may not be ordered unless the diagnosis is suspected.


The diagnosis can be made by performing cytology on blood aspirated from the pulmonary artery. A large wedge biopsy can be performed but this may be considered too invasive.


Differential diagnosis:

(1) venous thromboemboli

(2) lymphangitic tumor spread within the lung

(3) large macroscopic tumor emboli


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