Histopathologic specificity of systemic vasculitis.

A definitive diagnosis of vasculitis almost always requires histologic documentation of a true inflammatory disease of the blood vessels. Although each major type of systemic vasculitis may have its own characteristic and unique features, variability and overlaps still exist, and histopathologic specificity is rarely an absolute discriminator. The correct interpretation of biopsy specimens for the diagnosis of vasculitis remains more an art than a science; it is subject to such variables as the examining pathologist's interest and expertise, tissue selection and sample size, the age of the disease from onset to the time of biopsy, and whether there was drug treatment prior to the biopsy.