Pulmonary nocardiosis mimicking a lung neoplasm in an immunocompetent patient

After a chest X-ray, an immunocompetent 78-year-old non-smoker woman, presenting cough, dyspnoea and leucocytosis arrived at the lung cancer diagnosis program. Assessment was completed with a CT scan and a PET scan. Subsequently, a BAL and an EBUS were performed. Samples were negative for malignancy, but culture turned out positive.

Posterior-anterior (PA) and lateral X-rays showed a right hilar mass and associated partial atelectasis of the right upper lobe (Figures 1a and 1b).

CT scan revealed a hypodense mass in the right hilar region, likely necrotic, accompanied by a distal consolidation in the anterior segment of the upper lobe (Figures 2a, 2b and 2c). Lung neoplasia was the suspected diagnosis with these findings.

PET scan denoted hypermetabolism over the right hilar mass, the distal atelectasis/consolidation, and the mediastinal lymph nodes (Figure 3).

Follow-up imaging controls were performed by sequential radiography and CT. Under treatment with meropenem, progressive reduction of the lung mass and lymphadenopathies, as well as diminution of the consolidation, was seen. Residual atelectatic tracts with traction bronchiectasis and bronchial thickening in the right upper lobe remained two months after the initial CT (Figures 4a, 4b and 5).

Pulmonary nocardiosis (PN) is a rare opportunistic infection recognised in the past years, which is becoming more common due to the increased number of patients with depressed cellular immunity in our population and the improved diagnosis techniques developed [1,2]. Despite Nocardia spp. being usually reported in people suffering from HIV/AIDS, transplant recipients and patients under corticosteroid therapy, it can also affect immunocompetent individuals, mainly those with bronchiectasis, as in our case [3,4].

The clinical presentation of PN can vary widely and can mimic other lung conditions, such as pulmonary tuberculosis. It can occur as an acute, subacute or chronic disease [4]. Symptoms may include persistent cough, dyspnoea, fever, chest pain, unexplained weight loss or weakness.

The diagnosis typically includes a blend of clinical evaluation, laboratory tests and imaging studies. Concerning the last ones, chest radiography and CT are keys to diagnosis and follow-up [5].

Multiple radiographic patterns have been reported. Multilobar consolidation is probably the predominant manifestation. Foci of low attenuation areas with a rim enhancement on contrast-enhanced CT may reflect abscess formation. Cavitation might be associated in approximately 30% of the patients. Likewise, reticulonodular infiltrates may be demonstrated. It should be noted lymphadenopathies are not characteristic of this condition [4].

Endobronchial spread involves small centrilobular nodules, often associated with bronchial wall thickening and endobronchial debris. Disseminated PN consists on numerous different-sized nodules. Other accompanying, non-specific features include pleural thickening, pleural effusion or empyema necessitatis [4,5]. As in our patient, a solitary mass or nodule with central low attenuation and/or cavitation can be found.

Considering most of the patterns, an infectious process may be suspected. However, as concerning in our case, when PN is manifested as a solitary mass, a lung neoplasm might be presumed. Therefore, microbiological studies, in addition to cytological ones, are important when assessing solitary necrotic pulmonary lesions in immunocompromised patients.

When PN is clinically not suspected, the radiological presumption may guide blood culture, bronchial lavage, pleuropulmonary aspirates or even lung biopsies in order to isolate the bacteria and confirm the diagnosis [5].

First-line treatment is based on high-dose sulphonamide therapy. Empyema and chest wall abscesses may require surgical debridement or percutaneous drainage. Mortality rates are high. Time-to-diagnosis and an appropriate treatment are determining prognostic factors [6]. Recurrences after treatment are reported [4].

Take Home Message

Inflammatory-infectious processes can radiologically manifest similarly to lung neoplasms. Thus, the differential diagnosis of necrotic solitary pulmonary masses should be expanded.

All patient data have been completely anonymized throughout the entire manuscript and related files.