Pulmonary tumor thrombotic microangiopathy occurs when there are non-occlusive tumor cell microemboli with fibrointimal remodeling in small pulmonary arteries, veins and lymphatics. It rarely causes pulmonary hypertension.
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Epidemiology
Associations
At autopsy, approximately 25% patients with pulmonary tumor thrombotic microangiopathy are found to have an extrathoracic malignancy. Most commonly 6:
- hepatocellular carcinoma
- breast cancer
- renal cell carcinoma
- gastric adenocarcinoma
- prostate carcinoma
- choriocarcinoma
Diagnosis
The diagnosis of pulmonary tumor thrombotic microangiopathy rests upon histological confirmation, most commonly from a lung biopsy 6.
Clinical presentation
Progressive breathlessness is the key symptom of pulmonary tumor thrombotic microangiopathy.
Laboratory tests
- hypoxemia
- high A-a gradient
- raised D-dimer
Pathology
Thrombotic microangiopathy is a consequence of tumor cells metastasizing to the distal tiny arterioles, venules and lymphatics of the lungs. The embolized cells induce an intravascular procoagulant effect resulting in fibrocellular overgrowth of the intima and vasoconstriction. Occasionally, this proceeds to overt pulmonary hypertension.
Radiographic features
Structural imaging is usually unremarkable in pulmonary tumor thrombotic microangiopathy:
- chest radiography is usually normal
-
CT pulmonary angiography
- unremarkable for pulmonary emboli
- lymphangitis and/or vessel beading may be seen
-
V/Q scintigraphy
- many subsegmental perfusional defects
Treatment and prognosis
Pulmonary tumor thrombotic microangiopathy heralds a dismal prognosis. Although treatment of the primary tumor improves prognosis 6.
History and etymology
It was first described by Von Herbay et al. in 1990 2.
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