General and Systemic Histopathology, C601&C602
    Slide 106: Syphilitic aortitis
    You have to use your imagination a bit here.  The tissue you  have is just a little strip out of a large aneurysm of the thoracic aorta.  There is no way a complete section would fit on your slide. So, the first thing to do is to get yourself oriented as to where the lumen of the aorta is and where the adventitial surface is.  The atherosclerosis here is an incidental finding and not necessarily part of the reaction to the treponemal bugs.  After all, this person is entitled to more than one disease.

    See this slide with the virtual microscope.

    The inflammatory changes in the wall of the aorta are subtle and observed only in the outer layers of the muscular wall and the adventitia. The organism causes an obliterative "end arteritis," and what you see is the chronic inflammatory infiltrate surrounding the vasa vasorum. It is these smaller vessel that become the "target organ" of the treponemal bug. The H&E stain does not stain the organisms. It would take a special silver stain to highlight the typical corkscrew pattern of this pathogen. Even with this stain, they would be hard to find, as so few organisms are present. 

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