Figure 1. Remnants of Organized Thromboemboli



This opened, large pulmonary artery shows ridges (arrow) that remain after organization of thrombi. There are also strands ("violin strings") bridging orifices of branches. A postmortem clot bulges from a vessel near the center. It has a currant jelly appearance: no lines of Zahn were found on section of it.

Find 2 strands bridging orifices of branches.

Find the postmortem clot.

These ridges and strands produce turbulence that predisposes to in-situ thrombosis.

Figure 2. Acute Thromboembolus

The thromboembolus occluding this vessel shows branching lines of Zahn (asterisk) composed of fibrin-platelet aggregates, which are surrounded by a mixture of red and white blood cells. Note the absence of prominent vessels in the adventitia.


Figure 3. Organizing Thrombus and Older Intimal Thickening

Myofibroblasts migrate into the thrombus, recanalizing the lumen and causing intimal thickening. Hemosiderin pigment is often found (see clumps in the area of intimal thickening at the bottom).

Find the organizing thrombus.

Find the area of intimal thickening.



Thromboendarterectomy procedures remove the thrombus and the thickened intima, leaving the media (marked by arrows) intact.

Figure 4. Late Stage of Organization

This elastic van Gieson stain shows an old, partially recanalized thrombus with persistent fibrosis and small, sieve-like channels. Note the prominent collateral vessels in the surrounding adventitia.

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Strand (Violin string)





























Postmortem clot ("currant jelly" portion)
































Organizing thrombus






























Older intimal thickening