대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Actinomycosis

Radiologic Findings

Figure 1 Chest radiographs show focal well-marginated consoliation in RLL medial basal areas.
Figure 2-6. Chest CT scans reveal about 6.7-cm extent consolidation with mild peripheral GGO and internal low density with small cavitary portion in RLL medial basal segment. Right interlobar lymph node was enlarged, suggesting reactive hyperplasia.

Brief Review

Bronchoscopy of the patient revealed hyperemic and edematous mucosa with purulent scretions in the right lower lobe bronchi. On bronchoscopic biopsy, chronic inflammation with ulceration and actinomycosis colonies were identified.
Parenchymal patterns of pulmonary actinomycosis include a peripheral pulmonary nodule, mass or consolidation, all of which may or may not be cavitary or multifocal. Typical CT findings are reported as central areas of low attenuation within the consolidation in 62–75 % of cases and adjacent pleural thickening in 50–73 %. The disease initially manifests as a small, poorly defined, peripheral pulmonary nodule with or without interlobular septal thickening. The pulmonary nodule gradually increases to segmental air-space consolidation, which suggests bronchogenic spread of the disease. entral low-attenuation areas may be multiple and variable in size and show rim-like peripheral enhancement on enhanced CT.
At histopathologic correlation, the central low-attenuation area seen on CT represents microabcesss or necrotic material contained within ectatic bronchi. Confirmative diagnosis is based on histopathologic findings of Actinomyces colonies or sulfur granules (yellowish aggregation of clustered mycelia) or filamentous structures within the tissue specimen positive for Grocott-Gomori methenamine–silver staining.
The principal treatment of actinomycosis is long-term use of high-dose intravenous penicillin. The course of the disease depends largely on adequate and early antibiotic therapy.
Differential diagnoses of actinomycosis include necrotic lung cancer, tuberculosis, semi-invasive pulmonary aspergillosis, and other subacute necrotizing bacterial pneumonia.

References

1. Han JY, Lee KN, Lee JK, et al. An overview of thoracic actinomycosis: CT features. Insights Imaging 2013;4:245-252.
2. Kim TS, Han J, Koh W, et al. Thoracic Actinomycosis: CT Features with Histopathologic Correlation. AJR 2006;186:225-231.

Keywords