Malignancies Presenting With ANCA Positivity: Two Case Reports and Diagnostic Considerations

These cases highlight the potential for tumors to mimic AAV both clinically and serologically. They emphasize the importance of a careful differential diagnosis in patients with ANCA positivity, particularly when clinical progression is atypical or treatment response is suboptimal. The pathophysiological relationship between tumors and AAV remains unclear, but may involve common mechanisms such as neutrophil extracellular trap formation and autoantigen presentation of PR3 and MPO. Further studies are needed to elucidate these links and improve diagnostic accuracy in such complex presentations.