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
Table 2: Major Histopathological Features of Pulmonary Hypertensive Vascular Disease by Dana Point 2008 Clinical Classification [3]