Histologic Changes

The following sequence of photos shows the histologic features.

A. The pulmonic vegetation is composed of a proteinaceous coagulum that contains neutrophils and bacteria (dark blue). There was no evidence of organization to indicate healing.

B. Section of the thrombus in one of the segmental arteries shown on the previous page shows the same pattern as the vegetation, with PMNs and bacteria. Note that the inflammation has spread into the vessel wall (blue staining at arrows). The lack of parenchymal hemorrhage or infarction related to this lesion, which is several days old, signifies that heart failure was absent. Heart failure is a major factor that predisposes to infarction after pulmonary embolism of a segmental artery.

 

C. Higher magnification of the same artery shown in B. The infected thrombus (T) has caused transmural inflammation of the arterial wall (between 2 arrows). A portion of normal arterial wall (N) is also shown. Rupture of the vessel can occur as a result of such an infective arteritis. When an infected vessel dilates, it is called a mycotic aneurysm.

D. This vessel has an acute thrombus with some faint lines of Zahn (platelet-fibrin columns (arrow)), transmural arterial inflammation, and adjacent pneumonia with a necrotizing component (N) at the bottom left--the beginning of a septic infarct.

E. A section from a cavitary lesion shows numerous, dark blue bacteria in vessels and surrounding pneumonic consolidation of parenchyma that shows coagulative necrosis with preservation of tissue outlines.

Clinical summary Image 3

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