Actinomycosis is a chronic infection caused by grampositive anaerobic bacteria which is found worldwide [1]. Common features of actinomycosis infections include abscess, granulation, fibrous tissue, and the classical cutaneous sinuses with yellow/sulfur granular discharge [2].

Pulmonary actinomycosis is a rare but an important and challenging diagnosis to make and it is difficult to diagnose because of its appearance varies from similarities with bronchogenic carcinoma to pneumonitis like presentation resembling tuberculosis [3]. Pulmonary actinomycosis occasionally presents with massive or recurrent hemoptysis [3], [4]. These nonspecific clinical and radiologic findings make pulmonary actinomycosis difficult to diagnose and often lead to misinterpretation as malignancy, rather than an infective process [2].

The appearance of an actinomycotic lesion on chest radiograph and computed tomography (CT) scan resembled a tumor. The etiology of benign pulmonary opacity includes pneumonia, foreign body, tuberculosis, fungal infection, and autoimmune causes [1]. Here, we report a case of recurrent hemoptysis caused by pulmonary actinomycosis, which could be diagnosed using CT guided lung biopsy. However, with the absence of malignant cells and the features of actinomycoses on culture, the diagnosis of pulmonary actinomycosis was made.

A 71-year-old gentleman, who is a nonsmoker, presented to the respiratory outpatient department in our hospital with recurrent hemoptysis and constitutional symptoms. This is on a background of multiple basal cell carcinoma treated with topical agents and a positive family history of esophageal and gastric carcinoma. On examination, our patient was hemodynamically stable, afebrile, and examined well with good bilateral air entry, with no wheeze or crepitations.

Due to concerns for malignancy, imaging investigations were performed. The chest X-ray (CXR) revealed a patchy pulmonary consolidation in the basal aspect of the right upper lobe with pleural thickening at the right lung base (Figure 1). The chest CT scan showed a 45 × 25 mm spiculated lesion in the posterior segment of the right upper lobe and no associated lymphadenopathy (Figure 2). He then underwent two CT-guided core biopsy in his right upper lobe, which yielded negative for malignant cells on cytology but revealed chronic organizing inflammation with stromal fibrosis and granulation tissue suggesting an infective or inflammatory process. The histological analysis was negative for acid-fast bacilli or fungal elements.

The suspicious lung nodule was further worked up with a bronchoscopy with biopsy. There was notable distortion in the right middle lobe, however, the transbronchial brushings and right middle lobe lavage did not reveal any malignant cells or infection (Figure 3). To exclude pulmonary malignancy, a positron emission tomography (PET) scan was conducted (Figure 4). The spiculated lesion was detected in the posterior segment of the right upper lobe with an increased tracer uptake with a maximum standardized uptake value (SUV_max) of 11.71, which was highly suspicious for malignancy. A repeat CT-guided biopsy was performed in the right upper lobe and the histopathological assessment identified mixed chronic active inflammation with an aggregate of filamentous microorganisms with sulfur granules of Actinomyces and no malignant cells (Figure 5) and (Figure 6).

Our patient was then referred to a cardiothoracic clinic for further assessment. As pulmonary malignancy could not be excluded definitively, the decision for a right upper and middle lobe wedge resection was made. Once again, the histopathological assessment of the lung tissue showed bronchiectasis with multinucleate giant cells and abscess formation, with no evidence of malignancy. The operation was uneventful and he was discharged after a few days of hospital stay with no further oral antibiotics required in view of complete resection.

Actinomycosis is a rare, insidious, and persistent granulomatous, gram-positive microaerophilic anaerobic bacterial infection caused by Actinomyces species, which can be found as a commensal bacteria in our gastrointestinal and urogenital polymicrobial flora [3],[4]. Its virulence factor lies in its ability to produce biofilm hindering the efficacy of antibiotic therapy and further perpetuating its invasion process [5]. It commonly affects young- to middle-aged population with a male predisposition [6], [7]. It is more common in developing countries and has been associated with poor dental hygiene, alcoholism, and diabetes [8].

Thoracic actinomycosis accounts for 10–15% of actinomycosis cases and is the third most prevalent location after cervicofacial (60%) and abdominopelvic (20%) regions [5]. It can be subclassified further into pulmonary parenchymal, bronchial, and laryngeal actinomycosis [9]. Of these, pulmonary actinomycosis is the most common [10]. Bronchial actinomycosis is rare and may occur as a complication to endobronchial valve placement or foreign body aspiration [5], [11]. Laryngeal actinomycosis is also rare and is associated with a past history of laryngeal cancer and may present similarly to laryngeal cancer recurrence [12].

The clinical presentation of pulmonary actinomycosis includes: chest pain, productive cough, shortness of breath, and hemoptysis [13], [14]. Examination findings are usually nonspecific [15]. The imaging modality of choice is usually a CT scan of the chest which typically reveals a mass or peripheral consolidation and associated adjacent pleural thickening at an early stage, and may further demonstrate a transfissural extension or abscess formation at a later stage [16]. Chest roentgenology usually reveals the similar findings of a pulmonary mass [17]. Positron emission tomography scans are sometimes performed with the intention of differentiating malignant lesions from benign lesions including pulmonary actinomycosis [18].

Radiological features of thoracic actinomycosis

1. Infiltrative changes suggestive of aspiration pneumonitis or consolidation.
2. Fibronodular or cavitary parenchymal disease.
3. An intraparenchymal mass.
4. Pleural effusion or empyema (rare).
5. Involvement of chest wall soft tissue and destruction of adjacent bone with formation of sinus tracts to the skin.
6. Involvement of the mediastinum, pericardium, and myocardium.
7. Thoracic vertebral destruction.
8. Hypertrophic osteoarthropathy.

However, current studies reveal the standardized uptake value (SUV_max) of fluorodeoxyglucose that is arbitrarily pegged to a numerical value of 2.5 does little to distinguish malignant from benign lesions [19]. In our patient, the SUV_max was 11.71. In a case series, 10 of 11 patients were found to have a SUV_max value of more than 2.5 which further substantiates the point that clinicians should be aware that actinomycosis and other infections may present quite similarly with an increased fluorodeoxyglucose uptake like lung cancer, as this would affect our patients’ management [20].

The usefulness of bronchoscopy is usually limited to endobronchial actinomycosis, where a biopsy can provide a histopathological diagnosis [15]. A bronchoalveolar lavage can be performed and may show non-acid-fast, gram-positive, filamentous bacteria in the culture which points to actinomycosis [21].

Ultimately, the gold standard for diagnosis of pulmonary actinomyosis is histopathological assessment [4]. This can be obtained via CT-guided percutaneous biopsy or via open surgical resection [22]. The aim of both biopsy and surgical resection is to ascertain the diagnosis while preserving the remaining lung tissue [22]. On histology, the specimen should reveal inflammatory cellular infiltrates and colonies of filamentous microorganisms with sulfur granules, surrounded by necrotic tissue and inflammatory cells [15].

The management of pulmonary actinomycosis is complex and includes both medical and surgical interventions. The medication management involves the use of long-term beta-lactam antibiotics use over 3–12 months with follow-up appointments at the respiratory outpatient clinic [14], [23]. The termination of antibiotic use is patient-dependent and should only be ceased 1–2 months following both symptomatic and radiological resolution of actinomycosis [24]. The maintenance of good oral hygiene and alcohol reduction may further serve as a primary and secondary prevention of actinomycosis [7], [25]. While medical management is mostly successful, there have been previous instances when antibiotics have not been effective in the management of patients and surgical intervention is required [25]. The main indications for surgery include: failure of antibiotics therapy, management of hemoptysis, and ruling out lung malignancy [26], [27]. The patients who underwent surgical management had better clinical outcomes as opposed to patients on antibiotics regimen only [26]. The authors are agreement that in the setting of complex actinomycosis, surgical intervention should be considered at an earlier stage to mitigate the symptomatic duration, locate and manage the source of hemoptysis, as well as ensure that lung malignancy is not the cause of the presentation.

In conclusion, pulmonary actinomycosis is a rare with a nonspecific clinical presentation similar to lung cancer. The diagnosis of pulmonary actinomycosis requires a combination of clinical and radiologic features with microbiologic culture of specimens with identification of Actinomyces species with sulfur granules. Even with the diagnosis of actinomycosis, it is important to exclude potential coexisting lung malignancy. This can only be confirmed following symptomatic and radiological resolution with antibiotics regimen, or with clinical improvement on postoperative follow-up after surgical resection of the lung with histopathological substantiation.