Pulmonary actinomycosis and pulmonary nocardiosis mimicking lung cancer: A case series and narrative review.

Pulmonary actinomycosis and pulmonary nocardiosis are rare chronic respiratory infections that may closely resemble lung cancer due to their overlapping clinical, radiological, and bronchoscopic characteristics. This hybrid case series and narrative review aims to elucidate the presenting patterns, diagnostic pathways, management strategies, and practical implications of these infections in the differential diagnosis of lung cancer. We analyzed four consecutive cases managed at the Sotiria Thoracic Diseases General Hospital in Athens from 2021 to 2025, supplemented by eight additional cases identified through a review of Greek grey literature from the same period. In the 12 cases reviewed, patients commonly presented with cough, dyspnea, fever, hemoptysis, malaise, and weight loss. Chest imaging frequently revealed consolidation, cavitation, atelectasis, nodules, or mediastinal lymphadenopathy, often prompting an oncological evaluation. Bronchoscopic findings occasionally mimicked malignant submucosal spread, and increased fluorodeoxyglucose uptake added to the diagnostic uncertainty. Notably, one case exhibited coexistence of pulmonary actinomycosis with lung adenocarcinoma. Microbiological and histopathological evaluations confirmed the diagnoses, and most patients showed clinical and radiological improvement following prolonged targeted antimicrobial therapy. Given these findings, pulmonary actinomycosis and nocardiosis should be considered in patients with suspected lung cancer, particularly when infectious features coexist with mass-like or cavitary lesions. Careful tissue sampling, specialized microbiological testing, and structured follow-up are essential for excluding occult or coexisting malignancy.