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New diagnostic criteria for a disease that can cause later blindness will reduce false negative results arising from corticosteroid treatment. General pathologists will now be able to diagnose temporal arteritis (TA) (or giant cell arteritis (GCA)) after treatment has been started, if recent results are replicated in a larger multicentre randomised study.
The most reliable criteria for TA in its healing phase during treatment are a cuff of lymphocytes and epithelioid histiocytes where the outer muscle layer of the temporal artery and adventitia meet; large circumferential defects in, or absence of, the elastic lamina; and rather sparse, small multinucleate giant cells. This contrasts with the typically uniform granulomatous inflammation through the entire arterial wall in biopsy specimens taken before treatment.
Special stains are strongly recommended and immunohistochemical staining for CD‐68 to show epithelioid histiocytes; clinicians should inform pathologists about dosage and duration of treatment as these influence histological appearance.
The criteria were drawn up by ophthalmic pathologists from in depth analysis of 35 cases of TA in which biopsy specimens were obtained after corticosteroid treatment had started. The cases were drawn from a retrospective review of all cases of TA recorded over five years at the pathology laboratory of one eye institute in the United States.
The best treatment for TA is to give corticosteroids early, even before biopsy. As identification according to histological appearance of biopsy specimens is the diagnostic standard, there was a need to define cardinal histological features in the healing phase.
Font RL, et al. British Journal of Ophthalmology 2007;91:204–209.
Please visit the Journal of Clinical Pathology website [www. jclinpath.com] for a link to the full text of this article.