Simple case of consolidation with cavitation, in this case secondary to primary lung cancer in a smoker.

Differential diagnosis for a cavitating lung lesion is the mnemonic CAVITY:

• C: cancer 
  • bronchogenic carcinoma: most frequently SCC
  • cavitatory pulmonary metastasis(es): again most frequently SCC
• A: autoimmune; granulomas from 
  • Wegener's granulomatosis
  • rheumatoid arthritis (rheumatoid nodules) etc.
• V: vascular (both bland and septic pulmonary embolus)
• I: infection (bacterial/fungal)
  • pulmonary abscess
  • pulmonary tuberculosis
• T: trauma - pneumatocoeles
• Y: youth
  • CPAM
  • pulmonary sequestration
  • bronchogenic cyst