Subtleties in the histopathology of giant cell arteritis.

A temporal artery biopsy is typically obtained in cases of suspected giant cell arteritis (GCA). The differentiation between a "positive" versus a "negative" biopsy is sometimes not simple. Degrees of inflammation can vary from obvious, florid accumulations of giant cells to subtle pockets of non-granulomatous inflammation. Areas of normal pathology, or "skip lesions," may be interspersed within inflamed sections of the artery, resulting in a false negative diagnosis. Other features of the biopsy, such as the state of the internal elastic lamina and inflammation of the adjacent, smaller vessels, must also be evaluated and considered as possible signs of disease. Finally, some biopsies have an intermediate histopathologic appearance with mild inflammation and scarring, which may indicate prior treatment with corticosteroids, or "healed" arteritis. Careful examination and clinical correlation is therefore essential to evaluate for these subtleties, which can affect the final diagnosis.