Chest X-ray: cavitating lesions differential
Radiology   Wikipedia  
Wegener's syndrome
Embolic (pulmonary, septic)
Infection (anaerobes, pneumocystis, TB)
Rheumatoid (necrobiotic nodules)
Developmental cysts (sequestration)
Histiocytosis
Oncological
Lymphangioleiomyomatosis
Environmental, occupational
Sarcoid
Alternatively: L=Left atrial myxoma

 Mnemonic:
"If you see HOLES on chest X-ray, they are WEIRD"