Pulmonary actinomycosis is a necrotizing lung infection that can develop after aspiration of a foreign body. Approximately 50% of cases can mimic lung cancer.1

We report the case of a 76-year-old women diagnosed with right lower lobe (RLL) pneumonia in September 2014, treated with azithromycin 500mg/24hours for 1 week. After completing the course of antibiotics, she consulted due to dyspnea accompanied by cough with foul-smelling whitish sputum and fever. A chest computed tomography was performed (Fig. 1A), which showed heterogeneous pulmonary consolidation in the RLL, with no evidence of any obstructive central lesion. The patient received another cycle of antibiotics with amoxicillin/clavulanate acid (1000/200tid) for 14 days.

Fig. 1.

(A) Heterogeneous pulmonary consolidation in the right lower lobe, with no evidence of central lesion, associated with mural thickening. (B) Acute and chronic inflammation, forming focal abscesses, associated with a foreign body (fish bone), with Actinomyces superinfection, fibrosis and perilesional reactive changes.

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In September 2015, she presented with hemoptysis, and fiberoptic bronchoscopy was performed, revealing a “fibrin plug in a medial subsegment of the RLL”. Bronchial angiogram revealed a hypervascularized lesion in the right hilum, irrigated by a right bronchial artery originating in an intercostal trunk. The study was completed with a PET/CT, which showed the lesion in the RLL with a maximum standardized uptake value (SUV) of 4. Given the high suspicion of malignancy and the episode of hemoptysis, we decided to perform a surgical intervention. In view of the location of the lesion, right lower lobectomy was performed by thoracotomy.

The pathology report described mixed acute and chronic inflammation, forming focal abscesses, associated with a foreign body (fish bone), with Actinomyces superinfection, fibrosis and perilesional reactive changes (Fig. 1B).

Actinomycosis is a chronic suppurative infection caused by a group of anaerobic bacteria that are normally found in the flora of oropharynx and gastrointestinal tract. Approximately 15%–20% of cases diagnosed are located in the chest.3 The main symptoms associated with actinomycosis are: cough (63%), hemoptysis (36%) and recurrent pneumonias (27%).1 Most patients are men, over 55 years of age, with risk factors for aspiration pneumonia, such as diabetes mellitus, alcoholism, and poor dental hygiene.2,3

Pulmonary actinomycosis can mimic a malignant pulmonary process, so in some cases surgery is performed. Bates and Cruickshank4,5 published 85 cases of pulmonary actinomycetes, of which 7 underwent lung resection due to a clinical suspicion of lung cancer.

Treatment of pulmonary actinomycosis consists of prolonged intravenous antibiotic therapy with high-dose penicillin, for 3–4 weeks. Prognosis is generally more favorable when it is diagnosed and treated early.6

In patients with pulmonary lesions without a confirmed diagnosis of cancer, actinomycosis, even though it is rare, should feature in the differential diagnosis, particularly if there is a possibility that the patient may have aspirated a foreign body. Our case was a patient with a lung lesion caused by pulmonary actinomycosis after bronchoaspiration of a fish bone (not documented in her medical records) that mimicked a malignant process of the lung.