c-anca c-anca c-ancas, or pr3-anca, or antineutrophil cytoplasmic antibodies, are a type of autoantibody, an antibody produced by the body that acts against one of its own proteins. these antibodies show a diffusely granular, cytoplasmic staining pattern under microscopy. this pattern results from binding of ancas to antigen targets throughout the neutrophil cytoplasm, the most common protein target being proteinase 3 (pr3). for example, pr3 is the most common antigen target of anca in patients with granulomatosis with polyangiitis. in active granulomatosis with polyangiitis, c-anca is found over 90% of the time. other antigens may also occasionally result in a c-anca pattern. the granular, cytoplasmic staining pattern of c-anca