Imaging description

A mycetoma (fungus ball) is typically caused by Aspergillus superinfection of a pre-existing cavity or cyst. The mycetoma itself is characterized by a mobile soft tissue mass within a thick-walled cyst or cavity [1–3] (Figure 25.1). There is usually thickening of the pleura adjacent to the cavity. Common “cavities/cysts” that can be affected include those secondary to old granulomatous infections (tuberculosis, fungal), sarcoidosis (Figure 25.2), honeycombing in interstitial lung disease (Figure 25.3), bulla, and bronchiectasis from any cause. As such, the imaging findings in the lungs adjacent to or remote from the mycetoma may be influenced by the underlying disease. Mycetomas are usually solitary, but can be multiple and can occur in any location in the lung where a cyst/cavity has formed.

Importance

On the chest radiograph, a mycetoma may appear as a soft tissue mass in the lung and may be concerning for malignancy. However, the CT findings are usually diagnostic for mycetoma. Mycetomas typically have associated abnormal vascularity (bronchial artery hypertrophy) supplying the lesion and as such are predisposed to hemorrhage which can be significant. Approximately 10% of mycetomas will resolve spontaneously [1].