Table 2. Differential diagnosis of cavitary pulmonary nodules(1).

Benign cavitating pulmonary lesions		Malignant cavitating pulmonary lesions
Infectious	Bacterial necrotizing pneumonia: S. pneumoniae, H. influenza, K. pneumoniae, S. aureus Lung abscesses: Prevotella, Fusobacterium, and S. milleri group Uncommon infections: Actinomyces, Burkholderia pseduomallei, and Rhodococcus equi. Mycobacterial: M. tuberculosis, M. avium, M. intracellulare, M. malmoense, M. xenopi. Fungal: Aspergillus sp., Zygomycetes, Histoplasma capsulatum, Blastomyces dermatidis, Coccidioides immitis, Coccidioides posadasii, Paracoccidioides brasiliensis, Cryptococcosis neoformans, Penicillum marneffei, Pneumocystis jiroveci	Primary	Squamous Cell Carcinoma Lymphoma (particularly in HIV) Kaposi's Sarcoma Lymphomatoid granulomatosis
Autoimmune	Granulomatosis with polyangiitis Sarcoidosis Ankylosing Spondylitis Rheumatoid nodules Primary amyloidosis	Secondary	Metastatic tumors of squamous cell origin are more likely to cavitate than tumors of other origins
Pulmonary	Pulmonary Embolism Bronchiolitis Obliterans Organizing Pneumonia (up to 6% may have cavitary lesions (55)) Pulmonary Langerhans' cell Histiocytosis