Vascular endothelial growth factor (VEGF) is known as neurotrophic and angiotrophic factor; therefore, it induces proliferation of endothelial cells and increases permeability of the vessel wall [7, 8].
Several factors are known to cause apoptotic cell death such as oxidative stress and decreased neurotrophic or angiotrophic factors [3, 20, 21].
Muscle-derived stem cells can also act as mediators by releasing angiotrophic
, neurotrophic, chondrogenic, hematopoietic, adipogenic, osteogenic, and other growth factors, thus supporting and further activating endogenous mechanisms for regeneration.
The presence of cytokeratin-positive carcinomatous emboli and the marked pulmonary arterial and arteriolar intimal fibrocellular proliferation distinguish PTTM from other pathologic entities that could also cause pulmonary hypertension, including paraneoplastic thromboembolism, angiotrophic
lymphoma, lymphangitis carcinomatosa, epithelioid hemangioendothelioma, and intravascular bronchioloalveolar tumor of the lung.