Group 1: PAH |
1.1–1.4. Pulmonary plexogenicarteriopathy |
Early phase: |
● Medical hypertrophy |
● Cellular intimal proliferation of muscular pulmonary arteries |
● Appearance of muscle in normally nonmuscular arteries |
Late phase: |
● Concentric laminar intimal fibrosis |
● Loss of luminal vascular volume |
● Dilatation lesions (vein-like branches, angiomatoid lesions) |
● Plexiform lesions |
● Recanalization of arteries |
● Fibrinoid necrosis |
● Arteritis |
Group 1’: PVOD |
● Foci of intense congestion of pulmonary parenchyma |
● Patchy hemosiderosis associated with areas of congestion |
● Encrustation of elastin with iron and calcium salts in congested areas |
● Duplication of elastic laminae |
● Obliterative fibrosis of small veins and of venules, associated with congested areas |
● Abnormalities set against a background of normal or near normal lung tissue |
● Prominence of capillaries, associated with increased numbers of capillaries, often blurring the distinction from pulmonary capillary hemangiomatosis (group 1.4.2) |
Group 1’: PCH |
● Marked increase and prominence of capillary vessels in alveolar walls, interlobular septa, bronchovascular bundles, and pleura; masses of capillaries may bulge into lumina of airways and vessels |
● Associated features of PVOD in some cases |
Group 2: Pulmonary hypertension with left heart disease |
● Arterialization of large or middle-sized pulmonary veins |
● Interstitial edema and fibrosis |
● Hemosiderosis |
● Medial hypertrophy and adventitial thickening of pulmonary arteries |
Group 3: Pulmonary hypertension associated with lung disease and/or hypoxemia |
3.1 and 3.3–3.5. Hypoxic pulmonary vasculopathy |
● Intimal proliferation; adventitial thickening |
● Medial hypertrophy of muscular pulmonary arteries and arterioles, especially of smaller branches |
● Longitudinally oriented intimal smooth muscle cells |
● Slight medial hypertrophy of veins |
3.2. Pulmonary vasculopathy associated with interstitial lung disease |
● Features of hypoxic pulmonary vasculopathy |
● Eccentric intimal fibrosis of arteries and, to a lesser extent, veins |
Group 4: Pulmonary hypertension due to chronic thrombotic and/or embolic disease |
● Thromboembolic obstruction of distal pulmonary arteries |
Eccentric intimal fibrosis |
Recanalized organized thrombi forming bands and webs |
Fresh thrombi very rare |
Nota bene: lesion may be focal, requiring extensive search in multiple sections |
● Nonthrombotic pulmonary embolism |
Nonthrombotic material or tissue (foreign bodies, bone marrow) |
Fat embolism: many dilated optically empty blood vessels (down to capillary size) |
Group 5: Miscellaneous [sarcoidosis, compression of pulmonary vessels (adenopathy), tumor, fibrosingmediastinitis] |
● Heterogeneous group of disorders, some showing the features of congestive vasculopathy, some with features of post-thrombotic vasculopathy, some with combinations |