P ulmonary
Aliya N. Husain, M.D.
VIII. Vascular Lung Diseases
A. Thromboembolism, hemorrhage and infarction.
  1. Saddle thrombus is a blood clot which is seen at the bifurcation of the pulmonary artery. This results in sudden death with no pathologic change in the lungs.

  2. Smaller emboli lodge distally depending on their size. There is hemorrhage into the adjacent lung parenchyma.

  3. Infarction occurs when there is underlying heart failure or other diseases causing inadequacy of bronchial arterial supply. Infarcts are typically pyramidal with base at the pleura. The lung parenchyma dies (there are no nuclei in the septa) and there is often hemorrhage into the infarcted lung tissue.

  4. Emboli may contain tumor, infection, fat or bone marrow.

  5. Paradoxical embolus occurs when there is either an ASD or VSD through which the embolus goes to the left side of the heart and then into the systemic arteries.
B. Pulmonary edema
  1. This is usually not biopsied but is seen at autopsy or incidentally when biopsy is done for something else. There is pinkish pale material in interstitium and alveoli. When the cause is left-sided heart failure there are often hemosiderin-laden macrophages within alveoli (heart failure cells) which can also be coughed up and seen in sputum.
C. Pulmonary hypertension There is thickening of both intima and media of all pulmonary arteries. Atherosclerotic plaques can be seen in larger arteries. The changes can be graded from I to VI with the first three being reversible.

  1. Primary: The hallmark of primary pulmonary hypertension is the presence of plexiform lesions which are multiple channels lined by endothelium within small pulmonary arteries. Plexiform lesions are also seen in left to right shunts.
  2. Secondary: Plexiform lesions are rare. Underlying disease pathology is present.
D. Veno-occlusive disease
  1. The veins which run in the interlobular septa are occluded by fibrosis and may be difficult to identify on H&E sections. There are numerous hemosiderin-laden macrophages within the alveoli. There may also be recent hemorrhage.