DOI:10.2214/AJR.04.1749
AJR 2006; 186:225-231
© American Roentgen Ray Society
Thoracic Actinomycosis: CT Features with Histopathologic Correlation
Tae Sung Kim1,
Joungho Han2,
Won-Jung Koh3,
Jae Chol Choi3,
Myung Jin Chung1,
Ju Hyun Lee1,
Sung Shine Shim1 and
Semin Chong1
1 Department of Radiology and Center for Imaging Science, Samsung Medical
Center, Sungkyunkwan University School of Medicine, Gangnam-gu, Seoul 135-710,
South Korea.
2 Department of Diagnostic Pathology, Samsung Medical Center, Sungkyunkwan
University School of Medicine, 50, Ilwon-dong, Gangnam-gu, Seoul 135-710,
South Korea.
3 Department of Medicine, Division of Pulmonary and Critical Care Medicine,
Samsung Medical Center, Sungkyunkwan University School of Medicine,
Gangnam-gu, Seoul 135-710, South Korea.
Received November 11, 2004;
accepted after revision December 23, 2004.
Supported by grant R11-2002-103 from the Korea Science & Engineering
Foundation.
Address correspondence to J. Han.
Abstract
OBJECTIVE. Thoracic actinomycosis is a chronic suppurative pulmonary
or endobronchial infection caused by Actinomyces israelii, a
gram-positive anaerobic organism. We present the CT features of thoracic
actinomycosis with histopathologic correlation.
CONCLUSION. The typical CT feature of parenchymal actinomycosis is a
chronic segmental air-space consolidation containing necrotic low-attenuation
areas with frequent cavity formation. A broncholith can be secondarily
infected with Actinomyces organisms, resulting in endobronchial
actinomycosis. It usually manifests as a proximal endobronchial calcification
associated with distal obstructive pneumonia.
Keywords: broncholithiasis • CT • endobronchial actinomycosis • thoracic actinomycosis
Introduction
Thoracic actinomycosis is a chronic suppurative pulmonary or endobronchial
infection caused by Actinomyces species, most frequently
Actinomyces israelii, a gram-positive anaerobic saprophytic organism
in the oral cavity that historically was thought to be fungus, but now is
considered to be a branching filamentous bacterium
[1]. Actinomyces
infection typically follows aspiration of endogenous organisms of the
oropharynx into the lungs in persons with poor oral hygiene or from extension
of cervicofacial infections. The clinical manifestations of pulmonary
actinomycosis are productive cough, low-grade fever, and bloodtinged sputum.
The prognosis is generally good provided that the infection is recognized and
appropriate antibiotic therapy is instituted. A number of articles have
described the CT findings of pulmonary actinomycosis
[2,
3], and there also have been
reports of CT findings of endobronchial actinomycosis associated with a
foreign body [4] or
broncholithiasis [5,
6]. We present the CT features
of thoracic actinomycosis, including endobronchial actinomycosis, with
histopathologic correlation.
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Fig. 1A —51-year-old man with early stage parenchymal actinomycosis.
High-resolution CT image (1-mm collimation) shows poorly defined peripheral
pulmonary nodule in right lower lobe. Note surrounding areas of ground-glass
attenuation.
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Fig. 1B —51-year-old man with early stage parenchymal actinomycosis.
Photograph of wedge resection specimen shows poorly defined nodule
(arrows) formed by dense infiltration of many neutrophils and
lymphocytes. Note surrounding areas of intraalveolar fibrinous exudate with
some inflammatory cell infiltration (stars), which correspond to
areas of ground-glass attenuation on CT. (H and E, x1)
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Fig. 2 —61-year-old man with early-stage parenchymal actinomycosis.
Delayed contrast-enhanced CT image obtained with mediastinal window settings
shows small subpleural nodule in left upper lobe. Note central low-attenuation
area with peripheral enhancing portion of nodule and adjacent pleural
thickening (arrows). Actinomycosis was diagnosed using percutaneous
transthoracic core biopsy.
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Fig. 3A —61-year-old woman with parenchymal actinomycosis manifesting
as subsegmental consolidation. Contrast-enhanced CT image obtained with
mediastinal window settings shows subsegmental consolidation in posterior
segment of right upper lobe. Consolidation shows central low-attenuation area
with peripheral contrast enhancement. Note peripheral bronchiectasis
(arrow) and adjacent loculated pleural effusion.
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Fig. 3B —61-year-old woman with parenchymal actinomycosis manifesting
as subsegmental consolidation. Image of A obtained with lung window
settings shows triangular subsegmental consolidation contains ectatic bronchi
(arrow) with surrounding areas of ground-glass attenuation.
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Fig. 4A —42-year-old man with parenchymal actinomycosis manifesting as
necrotic peripheral mass. Delayed contrast-enhanced CT image obtained with
mediastinal window settings shows poorly defined subpleural mass with
low-attenuation area (arrow) in right lower lobe.
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Fig. 4B —42-year-old man with parenchymal actinomycosis manifesting as
necrotic peripheral mass. Image of A obtained with lung window settings
shows irregularly marginated mass with patchy areas of groundglass attenuation
and interlobular septal thickening (arrows).
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Fig. 4C —42-year-old man with parenchymal actinomycosis manifesting as
necrotic peripheral mass. Photograph of gross specimen from wedge resection of
right lower lobe shows peribronchial cavitary mass (arrows). Note
mild thickening of proximal bronchus (arrowheads). Scale: cm.
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Fig. 4D —42-year-old man with parenchymal actinomycosis manifesting as
necrotic peripheral mass. Photomicrograph of histopathologic specimen shows
bronchiectasis with surrounding areas of dense infiltration of inflammatory
cells and fibrosis. Note intraluminal granulation tissue (star) and
Actinomyces colonies (arrow) within ectatic bronchus.
Additional Actinomyces colonies (arrowheads) also are noted
within lung parenchyma. (H and E, x1)
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Fig. 5A —60-year-old man with parenchymal actinomycosis manifesting as
lobar consolidation. Contrast-enhanced CT images obtained with mediastinal
window settings reveal right upper lobe lobar consolidation. Consolidation
shows significant contrast enhancement with multifocal low-attenuation areas
(black arrowheads). Note bronchiectasis (arrow, A)
within consolidation and enlargement of right paratracheal lymph node
(white arrowhead, A).
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Fig. 5B —60-year-old man with parenchymal actinomycosis manifesting as
lobar consolidation. Contrast-enhanced CT images obtained with mediastinal
window settings reveal right upper lobe lobar consolidation. Consolidation
shows significant contrast enhancement with multifocal low-attenuation areas
(black arrowheads). Note bronchiectasis (arrow, A)
within consolidation and enlargement of right paratracheal lymph node
(white arrowhead, A).
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Fig. 6 —80-year-old man with parenchymal actinomycosis manifesting as
pulmonary mass. Contrast-enhanced CT image obtained with mediastinal window
settings shows mass replacing lingular division of left upper lobe. Note
multiple large areas of low attenuation within enhancing mass and adjacent
pleural thickening and ipsilateral dependent pleural effusion.
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Fig. 7A —67-year-old man with parenchymal actinomycosis that resolved
completely after treatment with antibiotic medication. Contrast-enhanced CT
image obtained with mediastinal window settings shows segmental consolidation
containing central low-attenuation area and several cavities.
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Fig. 7B —67-year-old man with parenchymal actinomycosis that resolved
completely after treatment with antibiotic medication. CT image obtained with
lung window settings at same level as A after 7 months of antibiotic
therapy with amoxicillin and clavulanic acid shows complete resolution of
consolidation with only residual parenchymal scarring (arrows)
evident.
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Fig. 8 —39-year-old man with parenchymal actinomycosis and pleural
effusion. Contrast-enhanced CT image obtained with mediastinal window settings
shows right middle lobe consolidation and moderate-sized pleural effusion.
Note central low-attenuation area (arrow) within consolidation and
mucoid impaction within bronchus (arrowhead).
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Parenchymal Actinomycosis
According to Cheon et al.
[3], chronic segmental
air-space consolidations that contain low-attenuation areas with peripheral
enhancement and adjacent pleural thickening are typical CT findings of
pulmonary actinomycosis. In an early stage of infection, the disease manifests
as a small, poorly defined, peripheral pulmonary nodule with or without
interlobular septal thickening (Figs.
1A,
1B, and
2). With the slow progression
of infection, the pulmonary nodule gradually increases in extent to manifest
as an air-space consolidation or a mass (Figs.
3A,
3B,
4A,
4B,
4C, and
4D). Although the consolidation
is usually segmental in distribution at the time of diagnosis, it can replace
a whole lobe at a later stage (Figs.
5A,
5B, and
6). Typically, the air-space
consolidation contains central areas of low attenuation with frequent
cavitation (Figs. 7A and
7B).
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Fig. 9A —57-year-old man with parenchymal actinomycosis manifesting as
chronic necrotizing pneumonia with transfissural extension. Contrast-enhanced
CT image obtained with mediastinal window settings shows extensive parenchymal
consolidation in superior segment of right lower lobe with areas of necrosis
and multiple small cavities. Note subcarinal lymphadenopathy (arrow)
and hypertrophied intercostal artery (arrowheads) supplying chronic
necrotizing pneumonia.
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Fig. 9B —57-year-old man with parenchymal actinomycosis manifesting as
chronic necrotizing pneumonia with transfissural extension. Coronal
reformation of contrast-enhanced CT image shows transfissural extension
(arrow) of necrotic consolidation from superior segment of right
lower lobe (large star) into upper lobe (small star). Note
thickening of adjacent interlobar fissure (arrowheads).
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Fig. 9C —57-year-old man with parenchymal actinomycosis manifesting as
chronic necrotizing pneumonia with transfissural extension. Photograph of
right pneumonectomy specimen shows large cavitary lesion in superior segment
of right lower lobe (large star), communicating with another cavitary
lesion in right upper lobe (small star) through transfissural
extension (arrow). Note thickening of adjacent interlobar fissure
(arrowheads). Scale: cm.
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Other associated CT findings include hilar or mediastinal lymphadenopathy,
bronchiectasis within the consolidation, localized pleural thickening, and
pleural effusion (Fig. 8). An
extensive consolidation sometimes can cross the adjacent interlobar fissure
(transfissural extension) and extend into the neighboring pulmonary lobe
(Figs. 9A,
9B, and
9C). Further progression of
the infection may involve the pleura and chest wall.
At histopathologic correlation, the central low-attenuation area seen on CT
represents microabscess or necrotic material contained within ectatic bronchi.
The peripheral enhancing portion of the consolidation represents chronic
inflammation with a varying degree of fibrosis. Confirmative diagnosis is
based on histopathologic findings of Actinomyces colonies or sulfur
granules (yellowish aggregates of clustered mycelia) or on filamentous
structures within the tissue specimen positive for Grocott-Gomori
methenamine-silver staining
[7].
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Fig. 10A —48-year-old man with actinomycosis associated with
bronchiectasis. High-resolution CT image obtained with 1-mm collimation shows
bronchial wall thickening and bronchiectasis in right lower lobe
consolidation.
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Fig. 10B —48-year-old man with actinomycosis associated with
bronchiectasis. Contrast-enhanced CT image obtained with mediastinal window
settings at lower level than A shows air-fluid level (arrow)
within bronchiectatic airway.
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Fig. 10C —48-year-old man with actinomycosis associated with
bronchiectasis. Photograph of specimen obtained from right lower lobectomy
shows bronchiectasis (stars) and bronchial wall thickening with
inflammation and fibrosis. Note Actinomyces colonies
(arrows) within lumen of ectatic bronchus.
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Fig. 11A —47-year-old man with endobronchial actinomycosis associated
with broncholithiasis. Contrast-enhanced CT image obtained with mediastinal
window settings shows small broncholith (arrow) obstructing bronchial
lumen that supplies superior segment of right lower lobe. More distally,
necrotic subsegmental consolidation containing mucoid material and another
broncholith (arrowhead) is seen with bronchial dilatation. Also note
small calcified hilar and subcarinal lymph nodes, suggesting previous
tuberculous infection.
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Fig. 11B —47-year-old man with endobronchial actinomycosis associated
with broncholithiasis. Contrast-enhanced CT image obtained at lower level than
A shows triangular subsegmental consolidation contains typical
low-attenuation area with adjacent pleural thickening
(arrowheads).
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Fig. 11C —47-year-old man with endobronchial actinomycosis associated
with broncholithiasis. Photomicrograph of histopathologic specimen of
endobronchial calcified nodule after decalcification shows numerous
filamentous structures (arrow) representing Actinomyces
organisms covering broncholith (B). (Grocott-Gomori methenamine-silver stain,
x200)
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The differential diagnosis of actinomycosis includes a necrotic lung
cancer, tuberculosis, semiinvasive pulmonary aspergillosis, and other subacute
necrotizing bacterial pneumonias.
Bronchiectatic Form
Actinomyces species tend to colonize devitalized tissue
[5]. Secondary actinomycotic
infection can involve a devitalized lobe or segment that already had been
damaged by previous tuberculosis or by other bacterial infections, resulting
in parenchymal destruction and bronchiectasis. A bronchial infection by
Actinomyces species exacerbates further the preexisting
bronchiectasis and bronchial inflammation and peribronchial parenchymal loss.
CT features include localized areas of bronchiectasis, irregular bronchial
wall thickening, and irregular peribronchial consolidation with or without
abscess formation (Figs. 10A,
10B, and
10C).
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Fig. 12A —56-year-old man with endobronchial actinomycosis associated
with foreign body (chicken bone). Contrast-enhanced CT image obtained with
mediastinal window settings shows small endobronchial calcification
(arrow) obstructing lumen of bronchus intermedius. Note surrounding
areas of low attenuation around endobronchial calcification, suggestive of
necrotic material.
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Fig. 12B —56-year-old man with endobronchial actinomycosis associated
with foreign body (chicken bone). CT image obtained with lung window settings
at lower level than A shows air-space consolidations and areas of
ground-glass attenuation in right middle and lower lobes, suggestive of
obstructive pneumonia.
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Fig. 12C —56-year-old man with endobronchial actinomycosis associated
with foreign body (chicken bone). Photomicrograph of specimen obtained from
bronchoscopic removal of endobronchial calcification reveals chicken bone,
which was surrounded by acute suppurative inflammation containing multiple
Actinomyces colonies in background of numerous neutrophils. (H and E,
x200)
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Fig. 13 —47-year-old woman with both parenchymal and endobronchial
actinomycosis associated with broncholithiasis. Contrast-enhanced CT image
obtained with mediastinal window settings shows small endobronchial
calcification (white arrow) obstructing lumen of posterobasal
segmental bronchus of left lower lobe. Masslike consolidation
(arrowhead) containing several cavities is also seen in anterobasal
segment of left lower lobe. Notice adjacent pleural thickening (black
arrow). Endobronchial actinomycosis was diagnosed by bronchoscopic
biopsy, and parenchymal actinomycosis was diagnosed by wedge resection.
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Endobronchial Actinomycosis Associated with Broncholithiasis
Rare cases of predominantly endobronchial actinomycosis have been reported
[4,
6,
8], including an article on
endobronchial actinomycosis associated with broncholithiasis
[6] and a case report on
endobronchial actinomycosis associated with a foreign body
[4].
Endobronchial actinomycosis associated with broncholithiasis likely results
from secondary colonization of a preexisting endobronchial broncholith by
aspirated Actinomyces organisms
[5]. The subsequent
inflammatory process results in progressive airway obstruction with distal
postobstructive pneumonia of the involved pulmonary lobe or segment.
Progressive shedding of Actinomyces colonies from the nidus
aggravates distal pneumonic consolidation further with subsequent abscess
formation.
The CT feature of endobronchial actinomycosis associated with
broncholithiasis is a proximal endobronchial calcified nodule (broncholith)
associated with distal postobstructive pneumonic consolidation of the involved
lobe or segment [6] (Figs.
11A,
11B, and
11C). Distal postobstructive
pneumonic consolidation shows a central low-attenuation area with or without
cavities. Mediastinal or hilar lymph nodes are enlarged frequently. Most cases
show evidence of an earlier tuberculous infection (e.g., calcified hilar and
mediastinal lymph nodes or calcified granulomata). In areas where tuberculosis
is endemic, the possibility of endobronchial actinomycosis should be suggested
when findings of broncholithiasis are present on CT.
Histopathologically, suppurative zones with multiple sulfur granules
comprising numerous branching filamentous organisms are identified around the
broncholith. Distal pneumonic consolidation seen on CT consists of acute
suppurative inflammation with abscess formation or organizing pneumonia with a
varying degree of fibrosis.
Endobronchial Actinomycosis Associated with a Foreign Body
Endobronchial actinomycosis can be associated with aspirated foreign
material, such as a chicken bone, a tooth, a fish bone, a grape seed, or a
bean [4]. The bronchial
infection results from direct aspiration of a foreign body contaminated with
Actinomyces organisms. CT may show a radiopaque endobronchial nodule,
in cases of an aspirated bone fragment, with distal obstructive pneumonia
(Figs. 12A,
12B, and
12C), which is similar to the
CT appearance of endobronchial actinomycosis associated with broncholithiasis.
Rarely, both the parenchymal form and the endobronchial form can be
encountered in one patient (Fig.
13).
In conclusion, the typical CT feature of parenchymal actinomycosis is a
chronic segmental air-space consolidation containing necrotic low-attenuation
areas with frequent cavity formation and peripheral enhancement. An
endobronchial broncholith can be secondarily infected with
Actinomyces organisms and a foreign body contaminated with
Actinomyces organisms can be aspirated, both resulting in
endobronchial actinomycosis. Endobronchial actinomycosis usually manifests as
a proximal obstructive calcified endobronchial nodule associated with distal
postobstructive pneumonia on CT.
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Abstract
Introduction
