Malignancy. Perhaps most important among noninfectious causes of cavitary lung lesions is malignancy, and a high index of suspicion is warranted given that it is commonly the first diagnosis to consider overall.2 Cavities can form in primary lung cancers (e.g. bronchogenic carcinomas), lung tumors such as lymphoma or Kaposi’s sarcoma, or in metastatic disease. Cavitation has been detected in 7%-11% of primary lung cancers by plain radiography and in 22% by computed tomography.5 Cancers of squamous cell origin are the most likely to cavitate; this holds true for both primary lung tumors and metastatic tumors.6 Additionally, cavitation portends a worse prognosis.7
Clinicians should review any available prior chest imaging studies to look for a change in the quality or size of a cavitary lung lesion. Neoplasms are typically of variable size with irregular thick walls (greater than 4 mm) on CT scan, with higher specificity for neoplasm in those with a wall thickness greater than 15 mm.2
When the diagnosis is less clear, the decision to embark on more advanced diagnostic methods, such as biopsy, should rest on the provider’s clinical suspicion for a certain disease process. When a lung cancer is suspected, consultation with pulmonary and interventional radiology should be obtained to determine the best approach for biopsy.
Rheumatologic. Less common causes of cavitary lesions include those related to rheumatologic diseases (e.g. granulomatosis with polyangiitis, formerly known as Wegener’s granulomatosis). One study demonstrated that cavitary lung nodules occur in 37% of patients with granulomatosis with polyangiitis.8
Although uncommon, cavitary nodules can also be seen in rheumatoid arthritis and sarcoidosis. Given that patients with rheumatologic diseases are often treated with immunosuppressive agents, infection must remain high on the differential. Suspicion of a rheumatologic cause should prompt the clinician to obtain appropriate serologic testing and consultation as needed.
(click for larger image)Figure 2. An Algorithmic Approach to Cavitary Lung Lesions
Pulmonary embolism. Although often not considered in the evaluation of cavitary lung lesions, pulmonary embolism (PE) can lead to infarction and the formation of a cavitary lesion. Pulmonary infarction has been reported to occur in as many as one third of cases of PE.9 Cavitary lesions also have been described in chronic thromboembolic disease.10
Other. Uncommon causes of cavitary lesions include bronchiolitis obliterans with organizing pneumonia, Langerhans cell histiocytosis, and amyloidosis, among others. The hospitalist should keep a broad differential and involve consultants if the diagnosis remains unclear after initial diagnostic evaluation.
Back to the Case
The patient’s fever and productive cough, in combination with recent travel and location of the cavitary lesion, increase his risk for tuberculosis and endemic fungi, such as Coccidioides. This patient was placed on respiratory isolation with AFBs obtained to rule out TB, with Coccidioides antibodies, Cyptococcal antigen titers, and sputum for fungus sent to evaluate for an endemic fungus. He had a chest CT, which revealed a 17-mm cavitary mass within the right upper lobe that contained an air-fluid level indicating lung abscess. Coccidioides, cryptococcal, fungal sputum, and TB studies were negative.
The patient was treated empirically with clindamycin given the high prevalence of anaerobes in lung abscess. He was followed as an outpatient and had a chest X-ray showing resolution of the lesion at six months. The purpose of the X-ray was two-fold: to monitor the effect of antibiotic treatment and to evaluate for persistence of the cavitation given the neoplastic risk factors of older age and smoking.
Bottom Line
The best approach to a patient with a cavitary lung lesion includes assessing the clinical presentation and risk factors, differentiating infectious from noninfectious causes, and then utilizing this information to further direct the diagnostic evaluation. Consultation with a subspecialist or further testing such as biopsy should be considered if the etiology remains undefined after the initial evaluation.