EXUBERANT ENDOTHELIAL-CELL GROWTH AND ELEMENTS OF INFLAMMATION ARE PRESENT IN PLEXIFORM LESIONS OF PULMONARY-HYPERTENSION

The plexiform lesion in primary pulmonary hypertension is a glomeruloi d structure forming channels in branches of the pulmonary artery. Thes e lesions have been considered an abnormal growth of modified smooth m uscle cells. We present immunohistochemical evidence in 10 cases of pl exogenic pulmonary hypertension that the plexiform channels and the co ncentric obliterative arteriopathy associated with these channels repr esent abnormal growth of factor VIII-related antigen-positive endothel ial cells. lit addition, these cells strongly expressed vimentin, a gr owth- and differentiation-related intermediate filament. Morphological ly and immunohistochemically, the lesions resembled the neovasculariza tion associated with the brain tumor glioblastoma multiform. Furthermo re, we noted an exclusively perivascular inflammatory cell infiltrate (but no vasculitis) in seven of the 10 cases with plexogenic arteriopa thy composed of T cells, B cells, and macrophages. Our findings indica te that the plexiform lesion may result from a deregulated growth of e ndothelial cells. The presence of perivascular inflammatory cells sugg ested that cytokines and growth factors may further influence the deve lopment of the plexiform lesion.