Location of Plexiform Lesions



Figure 1. Normal Supernumerary Branch of Pulmonary Artery: In addition to dichotomous branches seen on angiograms, the larger pulmonary arteries also have branches at right angles that do not fill during angiography. One such supernumerary branch is shown here. Note that its wall is much thinner than that of the parent artery.


Figure 2. Preacinar Plexiform Lesion

Here, a plexiform lesion is located adjacent to a large pulmonary artery, suggesting a supernumerary location. Although the lesion resembles a recanalized thrombus, the vessel wall is absent, having been destroyed before the development of the plexiform lesion.

Note the multiple fibrin-platelet thrombi in the lumens of the plexiform lesion.

Find a fibrin-platelet thrombus in the largest lumen.

Figure 3. Intra-acinar Plexiform Lesion

Here, a plexiform lesion (5 o'clock) is located in the intra-acinar region. Dilation lesions surround it.


Comment: The location of plexiform lesions in 5 lungs with idiopathic pulmonary hypertension and 6 lungs with hypertension related to congenital left-to-right shunts was studied. Lesions occurred both at supernumerary, preacinar branch points and at distal intra-acinar sites. Although plexiform lesions were found in both locations in each type of hypertension, there was a statistically significant predominance of preacinar plexiform lesions in lungs of patients with congenital heart disease (67%) compared to preacinar lesions in lungs of patients with idiopathic pulmonary hypertension (34%) [1]. The significance of this difference in distribution remains to be determined.

The fresh fibrin-platelet thrombi noted here in plexiform lesions are one manifestation of the clotting abnormalities that occur in PAH [2].

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Jamison B, Michel R. Different distribution of plexiform lesions in primary and secondary pulmonary hypertension. Hum Pathol 1995; 26:987-993. Abstract

2. Herve P, Humbert M, Sitbon O, Parent F, Nunes H, Legal C, Garcia G, et al. Pathobiology of pulmonary hypertension. The role of platelets and thrombosis. Clin Chest Med 2001; 22:451-458.

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Fibrin-platelet thrombus