Pulmonary arterial hypertension (PAH) is a human disease in which vascular remodeling can lead to the formation of plexiform lesions in terminal pulmonary arterioles. Various molecules are expressed by the diverse cell types within human plexiform lesions, including smooth muscle actin (SMA), von Willebrand factor (VWF), vascular endothelial growth factor (VEGF), VEGF receptor 2 (VEGFR2), collagen, and immune cells such as macrophages and CD8+ cells. Plexiform lesions rarely develop in the lungs of the laboratory mammals, but plexiform‐like complex vascular lesions (CVL) do develop spontaneously in the lungs of chickens from a PAH‐susceptible line. This study examined the expression of various molecules by the cells within CVL in chicken lungs. Paraformaldehyde fixed, paraffin embedded sections of lungs from 8‐ to 24‐week old male and female chickens were stained immunohistochemically using monoclonal or polyclonal antibodies. Cells within chicken CVL exhibited positive staining for SMA, VWF, VEGF, VEGFR2, collagen type III, macrophage and CD8 molecules. Foam‐like giant cells within the CVL stained positively as macrophages, whereas positive staining for VWF was detected in tufts of intimal cells and in the capillary endothelium of CVL. Immunohistochemical staining patterns within the CVL of PAH‐susceptible chickens combined with the close histological resemblance of CVL to plexiform lesions of human PAH patients further validates chickens from our PAH‐susceptible line as an excellent animal model of spontaneous plexogenic arteriopathy. Supported by NIH grant 1R15HL092517.