Hello Michael, et al.-
Monkeberg's Medial Calcific Sclerosis is simply dystrophic calcification at the internal elastic lamina. It is an isolated finding and has nothing to do with histologic identification of arteritis. Severe calcification encircling the majority of the artery can be an indication of calciphylaxis. Th bulkiness of the calcification can narrow the lumen and reduce blood flow. It is for this reason that I always include medial calcific sclerosis in the path report if I see it, and comment on the degree of calcification if extensive.
Breaks in the internal elastic lamina occur for many reasons, including hypertension, and are extremely common in elderly patients. Intermittent breaks in the lamina does not signify arteritis.
In order to histologically diagnose healed arteritis, criteria include a discontinuity of the internal elastic lamina for at least 180 degrees, along with disruption of the architecture of the intimal/medial interface in that region, suggesting damage due to a possible prior inflammatory event.
I tell our residents that if the biopsy shows active or healed arteritis, you can, of course, accept a diagnosis of temporal arteritis. A negative biopsy, however, does not exclude arteritis elsewhere. The biopsy is just a sample of a larger system. This is true even if you take the accepted steps in analyzing the biopsy as described by Dan Albert years ago (artery at least 2 cm long, cross-sectioned into 1 mm "barrels", at least 100 sections examined microscopically). Dan showed this protocol statistically should include "skip areas" of active inflammation separated by non-inflamed regions, thus making the histologic evaluation more valid. The primary key to diagnosis is the clinical symptomatology, and perhaps the response to steroids. Lab tests likewise, are supportive, but not indicative either for or against GCA. And of course, the pathologist must be handling and examining the specimen appropriately (never on longitudinal sections of the artery).
In the thousands of temporal artery biopsies I have examined, I have occasionally found cases with a giant cell or 2 attached to the calcification in Monkeberg's. However this is just a foreign body reaction to the calcium, is not accompanied by any additional inflammation, and is not "giant cell arteritis".
Thank you Claudia for also weighing in on this question.
Best regards,
Nick Hogan
Depts of Ophthalmology and Pathology
Director, Ocular Pathology Section
UT Southwestern Medical Center
Dallas, TX