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Pulmonary actinomycosis mimicking a lung metastasis from esophageal cancer; a case report
© The Author(s). 2018
Received: 8 January 2018
Accepted: 21 February 2018
Published: 27 February 2018
Actinomycosis is a rare bacterial infection caused by Actinomyces. The symptom of actinomycosis is nonspecific and radiological images present as a slow-progressive mass lesion similarly to malignancies. Thus, it is difficult to distinguish pulmonary actinomycosis from malignancies.
A 74-year-old male who had esophageal cancer and a pulmonary mass that was positive for 18F–fluorodeoxyglucose positron emission tomography/computed tomography was initially diagnosed with esophageal cancer with a lung metastasis because he was asymptomatic. However, aspiration of pleural effusion revealed that the pulmonary lesion was actinomycosis.
We present a case of pulmonary actinomycosis mimicking a lung metastasis from esophageal cancer. Diagnosis of asymptomatic pulmonary actinomycosis is difficult, and needle aspiration could be useful for a definitive diagnosis of pulmonary actinomycosis.
Actinomycosis is a rare chronic granulomatous infection caused by Actinomyces species. Actinomyces are facultative anaerobic Gram-positive bacteria . The symptom of actinomycosis is nonspecific and similar to those of other chronic suppurative chest diseases. On computed tomography (CT) and 18F–fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), pulmonary actinomycosis presents as a slow-progressive mass lesion similarly to malignancies. Non-specific symptoms and radiological images make diagnosis of pulmonary actinomycosis difficult [2, 3]. In previous case reports, pulmonary actinomycoses were occasionally resected as pulmonary neoplasms because of its difficult diagnosis . Here we report a case of pulmonary actinomycosis mimicking a lung metastasis from esophageal cancer.
Actinomycosis is a rare and chronic bacterial infection caused by Actinomyces species. Actinomyces israelii is one of the Actinomyces species. Actinomyces can colonize the cervicofacial, thoracic, abdominal, pelvic lesions, skin, brain and other organs. Pulmonary actinomycosis accounts for 15% of all actinomycoses , and is mainly caused by aspiration of oral saphrophytes into respiratory tracts . As actinomycosis can develop after dental care or aspiration, careful history taking is necessary for old ages. Sputum examination and culture is difficult to detect pathogenic bacteria, because Actinomyces are anaerobic and exist in normal oral cavity. Clinical symptoms of pulmonary actinomycosis include chest pain, chronic cough, hemoptysis, fever and chill , but actinomycosis frequently has no symptoms. Nonspecific symptoms or no symptoms make a definitive diagnosis difficult. Radiologically, pulmonary actinomycosis presents as a slow-progressive consolidation or mass-like shadow. Pulmonary actinomycosis often has central attenuation area or dilation bronchiole shadow on CT. Central low attenuation area consists of one or more, round or oval low attenuation area at the center of the shadow , which is characteristic of pulmonary actinomycosis. 18F–FDG PET/CT is useful for detecting malignancies including metastases in the whole body, but various inflammations and infections also have FDG uptake [2, 3]. The interpretation of PET/CT finding needs to be careful with primary malignant lesions. Even experienced physicians could delay diagnosis or misdiagnose with tuberculosis or lung cancer . For a definitive diagnosis, biopsy is often required. However, success of CT-guided, ultrasound-guided, or bronchial biopsy is dependent on the location of pulmonary mass . Lung resection was occasionally performed as a diagnosis of pulmonary neoplasm and pulmonary actinomycosis was diagnosed by the pathology of the resected lung specimens [9, 10]. Regarding to the therapy of actinomycoces, almost all Actinomyces is sensitive to penicillin. For Actinomyces forming chronic granulation, penicillin in high doses is usually needed for long duration (6–12 months) to prevent relapse. Risk factors associated with the acquisition of Actinomyces are diabetes mellitus, male sex, and immunosuppressive condition such as a use of steroid and alcoholism . In this case, the patient’s long-term diabetes mellitus is considered to be a risk factor for infection of Actinomyces. The patient had primary esophageal cancer and past history of primary pulmonary adenocarcinoma, which made a diagnosis difficult. However, a high fever after starting chemotherapy gave us a clue of the infection and prompted us to perform needle aspiration of the pleural effusion.
Even though rare, pulmonary actinomycosis should be included in differential diagnosis of PET/CT positive pulmonary mass without any symptoms. Especially, if a patient has other primary malignant lesions, it is difficult to distinguish pulmonary actinomycosis from a lung metastasis. If available, needle aspiration could be useful for a definitive diagnosis of pulmonary actinomycosis.
We thank Dr. Matsuo for advices on diagnosis of asymptomatic pulmonary actinomycosis.
None (for all authors).
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All the data regarding the findings are available within the manuscript.
MN participated in diagnosis and drafted the manuscript. TM and TK participated in diagnosis. AF and HS supervised this manuscript. All authors read and approved the final manuscript.
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