Aspergillomas are mass-like fungus balls that are typically composed of Aspergillus fumigatus and are a non-invasive form of pulmonary aspergillosis. It usually falls under the subgroup chronic pulmonary aspergillosis.
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Terminology
Although the term mycetoma is frequently used to describe these fungal balls, it is an incorrect term to use 5,6.
Epidemiology
Aspergillomas occur in patients with normal immunity but structurally abnormal lungs, with pre-existing cavities. Demographics will, therefore, match those of the underlying condition, such as 2:
- pulmonary tuberculosis: most common, accounting for 25-80% of cases depending on the prevalence of tuberculosis in the population 2,3
- pulmonary sarcoidosis
- bronchiectasis from any cause
- other pulmonary cavities
Clinical presentation
Most aspergillomas are asymptomatic. Occasionally due to surrounding reactive vascular granulation tissue, hemoptysis may be present. Occasionally, erosion into a bronchial artery may lead to life-threatening hemoptysis 1.
Pathology
An aspergilloma is a mass-like collection of fungal hyphae, mixed with mucous and cellular debris, within a cavity, the walls of which demonstrate vascular granulation tissue 1,2.
Distribution
Aspergillomas typically occur in the cavities of post-primary pulmonary tuberculosis. Therefore, they are most frequently found in the posterior segments of the upper lobes and the superior segments of the lower lobes.
Radiographic features
Plain radiograph
An aspergilloma can be seen as a mass within a cavity. The mass is typically spherical or ovoid. The air around the aspergilloma takes a crescentic shape, termed the Monod sign, which is distinct from the air crescent sign in recovering invasive aspergillosis. On different positioning of the patient, the mass can be shown to be mobile.
CT
CT better demonstrates the plain radiographic findings of a rounded mass within a cavity. The Monod sign of air around the mass is usually present and mobility of the mass can be demonstrated between prone and supine positioning. On occasion the mass may entirely fill the cavity, thus taking on the shape of the cavity, obliterating the surrounding air crescent and no longer being mobile 2. The mass is soft tissue attenuation but calcification is not uncommon.
Due to the inflammation and vascular granulation tissue formation, the bronchial arteries supplying the wall can be enlarged 2. The adjacent pleura may well be thickened.
Treatment and prognosis
An asymptomatic aspergilloma does not necessarily require treatment, and the cavity is essentially isolated from any systemic administration of antifungal 3.
In the setting of brisk hemoptysis, angiography may be performed on an emergency basis and selective bronchial artery embolization can be life-saving. Failing this, or in cases of repeated hemoptysis, surgical excision with a lobectomy remains the gold standard 3.
The mortality rate varies widely, but in more recent series is low, even where requiring surgery 3.
Differential diagnosis
When classical in appearance there is little differential. If the mass fills the cavity completely then the differential is that of a solitary pulmonary nodule.
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