Cavitary lung lesion

Today we discussed the approach to a cavitary lung lesion. Some points:

Definition:
Lucent areas within the lung that may or may not contain an air-fluid level, that is surrounded by a wall, which may be of varied thickness. They can be thought of as "holes" in the lung with various changes in the surrounding parenchyma.

Generally results from necrosis of lung parenchyma or central necrosis of an existing nodule or mass.

Useful imaging characteristics to help with differential
1) Surrounding lung parenchyma- within consolidation suggests abscess
2) Wall thickness ( if less than 1mm, almost always benign, if over 15mm almost always malignant
3) Contour- nodular or irregular suggest malignancy; smooth suggests infection or inflammation


Differential diagnosis and predisposing factors

1) Necrotizing infections:
Bacterial: Anaerobes (seizures, decreased LOC, poor dentition, other risk of aspiration), Aerobes (necrotizing pneumonia; St. aureus, st. pneumo, legionella, pseudomonas, others)
Mycobacterial: Tuberculous and non-tuberculous
Fungal: Aspergillus, mucormycosis, endemic mycoses (blasto, coccidio, histo)

2) Malignancy
2-10% of bronchogenic carcinomas have cavitation on CXR.
Germ cell tumors
Lymphomas
Metastases (rarely)

3) Inflammatory
Vasculitis, especially Wegener's granulomatosis, can present with cavitary lesions.
Rheumatoid arthritis
There is a cavitating variant of sarcoidosis

4) Others:
Bronchiectasis, bullae or cysts with air-fluid level, pulmonary embolism with infarction.

History and physical are targeted to this differential. Useful investigations include CT chest, bronchoscopy with cultures and cytology, and lung biopsy if etiology still unclear.

Some links:
Click here for a NEJM clinical pathological case on cavitary lesions
Click here for a good radiology textbook chapter on cavitary lesions