Cavities in the Lung in Oncology Patients: Imaging Overview and Differential Diagnoses

Ritu R. Gill, MD; Shin Matsusoka, MD, PhD; Hiroto Hatabu, MD, PhD

Disclosures

Appl Radiol. 2010;39(6):10-21. 

In This Article

Nonmalignant Cavitary Diseases

Tuberculous, nontuberculous, bacterial and fungal infections can present with cavity formation and ascertaining the most likely diagnosis is vital in the management of the oncology patients, especially the post bone-marrow transplant population.

Mycobacterium Tuberculosis Infection

Cavitation is common in post primary tuberculosis and is usually located in the apical and posterior segments of the upper lobes and superior segments of the lower lobes.[32,33] The prevalence of cavities on plain chest radiographs varies in 30% to 50% of patients. Cavities can vary widely in size and have been reported to have both thick and thin walls.[34–36] Multiple cavities are often present and frequently occur in areas of consolidation.[34,37] The presence of cavitation is associated with a greater degree of infectiousness, likely due to higher organism burden.[38] The number and maximum size of cavities can correlate with the numbers of acid-fast bacilli (AFB) in sputum.[39] Although the morphological findings of cavitation in patients with post primary tuberculosis are hardly distinguishable from malignant cavitary lesions (Figure 7), the presence of adjacent tree-in-bud lesions,[40] or satellite nodules may help in differentiating tuberculosis from malignancy. The efficacy of dynamic CT and magnetic resonance imaging (MRI) has been reported to differentiate between malignant tumor and tuberculoma,[41.42] but it has not been clarified whether the presence of cavitation affects that efficacy or not.

Figure 7.

Metastatic pancreatic cancer on chemotherapy. Axial CT shows a thick-walled cavity in the left upper lobe with surrounding linear and nodular parenchymal opacities. Tuberculosis should be considered in the differential diagnosis.

Factors that depend on the host play an important role in the prevalence of cavitation of tuberculosis. In patients with acquired immunodeficiency syndrome, cavitation is less frequent,[43,44] whereas cavitation is highly prevalent among diabetic patients with tuberculosis,[45] and multiple small, irregular cavities also have been reported on CT scans.[46]

Nontuberculous Mycobacterial Infection

Nontuberculous mycobacteria including Mycobacterium kansasii and Mycobacterium avium-intracellularecomplex can cause pulmonary infections that are associated with cavities. As for Mycobacterium avium-intracellulare complex, 65% of patients have cavitation (Figure 8), and the presence of cavity on CT is associated with positive sputum culture.[47] The cavities are relatively small and thin walled.[48,49] Sometimes it is difficult to differentiate from cavitary metastasis. However, other typical CT findings, including nodules with associated bronchiectasis particularly in the lingula and right middle lobe, may help in the diagnosis.[47,50]

Figure 8.

A patient with non-Hodgkin's lymphoma with Mycobacterium avium intracellulare infection. Axial CT (A and B) shows a cavitating lesion with tree-in-bud nodules. Centrilobular nodules are often seen with infections caused by atypical mycobacteria.

In patients with Mycobacterium kansasii, the frequency of cavitation is high (87% to 96%) and cavitation is visible even on plain radiographs. Cavitary lesions may be single or multiple with thin walls, predominantly in the upper lobes.[51,52]

Fungal Infections

The radiological presentations of pulmonary fungal infections vary depending on the patient's immune conditions. In the immunocompetent patient, fungal infections are uncommon, however, cavitation in fungal infection is not rare and can mimic malignant cavity. Thus, occasionally differentiating a fungal cavity from malignant cavity is difficult.

An aspergilloma represents growth of aspergillus within a pre-existing lung cavity. The typical radiographic finding is a rounded soft tissue within a previously existing cavitary lesion such as tuberculosis cavity (Figure 9). The appearance of the soft tissue can be similar to malignant lesion. It has been reported that the enhancement of the intramural soft tissue on CT implies malignancy, while the findings of adjacent bronchiectasis, a dependent location and positional mobility suggest aspergilloma.[53]

Figure 9.

Bronchogenic carcinoma of the left upper lobe post radiation with a mycetoma in the bronchopleural cavity in the left apex. PA radiograph (A) shows post radiation changes and the mycetoma in the left apex. Axial CT (B) confirms the mycetoma in the left apical cavity.

The radiological findings of cryptococcosis also depend on the immune status of the patient. The most common findings in immunocompetent patients are focal infiltration and nodules. Cavitation can be detected in 14% to 42% within consolidation and nodules in immunocompetent patients (Figure 10). There are no specific findings that can differentiate cavitary cryptococcosis from malignant cavitary lesion. On the other hand, cavitation is significantly less common in severely immunocompromised patients, particularly in HIV patients, than in immunocompetent ones.[54–56] However, in mild to moderately immunocompromised patients such as diabetes, liver cirrhosis, and corticosteroid therapy, cavitation is observed more frequently (62.5% of patients).[54]

Figure 10.

Hodgkin's lymphoma post bone marrow transplant, presenting with fever and seizures. The patient was diagnosed with Cryptococcus infection. Axial CT shows a peripheral cavitary lesion, which was biopsyproven to be Cryptococcus.

Cavities with thick or thin walls are seen in patients with pulmonary blastomycosis, histoplasmosis, coccidioidomycosis, and mucormycosis.[57–60] These cavitary lesions can be solitary or multiple. Unfortunately, there are no specific findings that can differentiate between these cavitary fungal nodules and malignant cavities.

Bacterial Infections

Cavitation can be seen with community-acquired bacterial pneumonia, particularly Klebsiella pneumoniae pneumonia (Figure 11) and Staphylococcus aureus pneumonia. However, most cases of community-acquired bacterial infection present symptomatic inflammatory changes such as productive cough and high-grade fever. In addition, rapid change of ill-defined consolidation on plain chest radiography suggests bacterial pneumonia rather than malignancy.

Figure 11.

Patient with leukemia presenting with fever and chills. Chest PA radiograph (A) and axial CT (B) of the thorax show a well-defined cavity with an air-fluid level suggestive of a lung abscess, bronchial lavage cultures were positive for Klebsiella.

Pulmonary actinomycosis usually results from aspiration of infected material containing actinomyces.[61] Cavitation in actinomycosis is a common finding on CT in 62% to 75%.[62,63] Pulmonary actinomycosis is relatively asymptomatic and progresses gradually with nonproductive cough or low-grade fever. In addition, chest-wall invasion, transfissural extension, and hilar or mediastinal lymphadenopathy can be occasionally observed.[64] Segmental consolidations that contain low-attenuation areas with peripheral enhancement and adjacent pleural thickening suggest pulmonary actinomycosis.[62]

Septic embolism usually presents with severe symptoms including high-grade fever and dyspnea, however, asymptomatic cases also have been reported.[65] Cavitary nodule located in the lung periphery is frequent and can be detected in 85% of instances on CT.[66] The appearance can be confused with cavitary malignant lesion such as multiple pulmonary metastases (Figure 12). Classically, "a feeding vessel sign," in which a distinct vessel is seen leading to the center of a pulmonary nodule, has been reported as a typical finding of septic emboli.[67] however, the feeding vessel sign also can occur in pulmonary metastasis.[68] In addition, a recent study showed that most of these vessels coursed around the nodule and some were pulmonary veins.[69]

Figure 12.

Patient with pancreatic cancer with an infected central venous catheter presenting with septic emboli. Axial CT image shows cavitating nodules in both right and left lower lobes. The lower lobe predominance, peripheral location of the nodules and a pulmonary vessel leading to the nodule in this clinical setting are suggestive of septic emboli. Hematogenous metastases also have similar distribution and may demonstrate the "feeding vessel sign."

Meanwhile, the pneumonic type of bronchoalveolar cell carcinoma shows lobar consolidation, and both bacterial pneumonia and the pneumonic type of bronchoalveolar cell carcinoma can have cavitations. Thus, it is often difficult to differentiate from bacterial pneumonia (Figure 13). In old times, the "angiogram sign," in which branching pulmonary vessels could be visualized normally within areas of consolidation on contrast-enhanced CT, was reported as a specific sign of the pneumonic type of bronchoalveolar cell carcinoma,[70] however, it also can be seen in pneumonia.[71] A recent study showed that consolidation on CT may suggest infectious pneumonia rather than the pneumonic type of bronchoalveolar cell carcinoma when bronchial wall thickening, proximal to the lesion, and pleural thickening, associated with the lesion, is evident.[72]

Figure 13.

Adenocarcinoma with bronchoalveolar-cell features diagnosed in a patient presenting with bronchorrehea. Axial CT image shows a dominant left upper lobe mass with surrounding ground-glass opacification and irregular cavity. Multifocal ground-glass opacities are seen in the right lung secondary to transbronchial spread of disease.

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