Diagnostic histopathology of major systemic and pulmonary vasculitic syndromes.

The vasculitides are a heterogeneous group of diseases with protean and frequently overlapping clinical and pathologic manifestations. They are difficult to classify because the etiology and pathogenesis of most vasculitides are unknown. A definitive diagnosis of vasculitis almost invariably requires histologic documentation of the disease. Although each major vasculitic syndrome may have its own unique and characteristic histologic features, the correct interpretation of biopsies still depends on such factors as the pathologist's interest and experience, tissue selection, sample size, chronologic age of the disease process, and any prior treatment at the time of the biopsy.