[Case no 5. Pseudotumor presentation of pulmonary granulomatosis with polyangiitis].

Granulomatosis with polyangiitis (GPA) (formerly Wegener's disease) is a systemic ANCA (anti-neutrophil cytoplasmic antibody) vasculitis that frequently affects the lungs. We report the case of a patient with isolated pulmonary GPA and a pseudotumoral clinical presentation. In the presence of the major histopathological criteria for GPA (vasculitis lesions, parenchymal necrosis, and granulomatous inflammation), a diagnosis of GPA can be proposed after excluding the main differential diagnoses (infection, necrotizing sarcoidosis granulomatosis, eosinophilic granulomatosis with polyangiitis, and lymphomatoid granulomatosis). However, these criteria are often absent on transthoracic biopsy, justifying a surgical biopsy in cases of high clinical probability. The final diagnosis of GPA is based on the integration of clinical, imaging, anatomopathological, and biological data (possible presence of ANCA).