Granulomatosis With Polyangiitis (GPA) Mimicking Metastatic Malignancy.

Granulomatosis with polyangiitis is a rare vasculitis characterized by necrotizing granulomatous inflammation affecting small blood vessels. It often presents with pulmonary masses and nodules, mimicking malignancy in imaging studies. Distinguishing granulomatosis with polyangiitis from cancer is crucial due to differing treatment approaches and prognoses.