Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): This is a form of vasculitis that affects small- and medium-size vessels in many organs, including the lungs. It is characterized by the presence of necrotizing granulomas and is often associated with anti-neutrophil cytoplasmic antibodies (ANCA). The lung involvement can manifest as necrotizing granulomas, making it a leading consideration in the differential diagnosis.

Tuberculosis: Although typically associated with caseating granulomas, some forms of tuberculosis can present with necrotizing granulomas, especially in immunocompromised patients or in certain extrapulmonary forms.
Sarcoidosis: While sarcoidosis is more commonly associated with non-necrotizing granulomas, rare cases can exhibit necrotizing features, particularly in the lungs.
Invasive Aspergillosis: In immunocompromised patients, invasive aspergillosis can cause necrotizing lesions in the lung that may mimic granulomas.

Lung Cancer: Although less common, certain types of lung cancer (e.g., squamous cell carcinoma) can mimic necrotizing granulomas on imaging and histology. Missing a diagnosis of cancer could have devastating consequences.
Infectious Diseases (e.g., Pneumocystis jirovecii pneumonia, Nocardia): These infections can present with necrotizing lesions in the lung, particularly in immunocompromised patients, and require prompt treatment to prevent severe outcomes.

Churg-Strauss Syndrome (Eosinophilic Granulomatosis with Polyangiitis, EGPA): A form of vasculitis characterized by asthma, eosinophilia, and granulomatous inflammation, which can rarely present with necrotizing granulomas in the lungs.
Rhinoscleroma: A chronic granulomatous infection caused by Klebsiella rhinoscleromatis, which can very rarely affect the lungs and present with necrotizing granulomas.
Berylliosis (Chronic Beryllium Disease): A lung disease caused by exposure to beryllium, characterized by granulomatous inflammation, which can occasionally exhibit necrotizing features.