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November 5, 2021

Vascular Changes On Thick Sections

vasculitis

Low power image:

The small arteriole (large arrow) shows thickening and hypercellularity of its wall.  The hypercellularity is in part due to the presence of chronic cells. Note the marked loss of myelinated axons in the two nerve fascicles (small arrows)

 

This 50-year-old patient presented with microscopic hematuria, weight loss, and difficulty with gait. Electrodiagnostic studies are reported to have demonstrated features of a multifocal sensorimotor neuropathy. Laboratory studies showed positive cANCA, elevated ESR and CRP, and normal CPK. The patient was treated with steroid and azathioprine prior to nerve biopsy.

 

Which of the following morphologic features in Figures 1- 5 support a pathologic diagnosis of vasculitis?

A. Loss of elastic lamina

B. Fibrinoid necrosis

C. Inflammation

D. All of the above

 

vasculitis

Medium power image:

Can you identify the irregular wavy blue line toward the outside of the blood vessel wall.  This is the elastic lamina. There is partial loss of this (4 o’clock to 7 o’clock).

Additional things to notice include the thickening of the blood vessel wall, narrowing of the vascular lumen, and increase in small blood vessels surrounding the small artery (neovascularization).

vasculitis

High power image:

Up close view to better show  the area with partial loss of elastic lamina.

Also note the small endothelial lined vascular spaces surround the blood vessel (neovascularization).

vasculitis

High power image:

In a different section of this small artery multiple micro-lumens are present.  This indicates prior vascular thrombosis/occlusion of the original lumen and subsequent recanalization.  Note that these new lumens are within the circle formed by the elastic lamina. 

Lower power image:

While hematoxylin and eosin stained sections are what a Pathologist’s eyes are most used to seeing, it is good to be able to recognize morphologic detail in other type of stained sections, including toluidine blue stained thick sections which have some of the best light microscopic morphologic resolution.

 

Answer: All of the above

The classic morphologic triad of vasculitis (arteritis in this case) includes inflammation within and surrounding the blood vessel wall, destruction of the internal elastic lamina providing evidence for vessel wall damage, and fibrinoid necrosis which is felt to be due to destruction of the endothelial cells and inner aspect of the involved blood vessel.

Other changes include neovascularization indicating formation of new capillaries in response to tissue injury, hemosiderin pigment deposition indicating prior leakage of red blood cells from blood vessels and breakdown of hemoglobin, and micro-lumen formation indication recanalization of a thrombosed/occluded blood vessel.