Not All That Glows Is Malignant: Actinomycosis as a Rare Mimic of Lung Cancer (2022)

Type of publication:Conference abstract

Author(s):*Ekhelikar S.; Muthusami R.; *Orme R.; *Ahmad N.

Citation:American Journal of Respiratory and Critical Care Medicine. Conference: International Conference of the American Thoracic Society, ATS 2022. San Francisco, CA United States. 205(1) (no pagination), 2022.

Abstract:Introduction: Pulmonary actinomycosis is a rare bacterial infection that can mimic malignant and chronic suppurative lung conditions, and therefore is often misdiagnosed initially as one of the more common differential diagnoses. The challenge lies in diagnosing this condition prior to surgery as it is completely curable with antibiotics. Case description: A 48 year old man, cigarette smoker and previous intravenous drug user, presented with exertional breathlessness, persistent cough and night sweats. There was no fever or weight loss. A Chest Xray (CXR) and Computerised Tomography (CT) scan showed a left upper lobe cavitating lesion leading to differential diagnoses of bronchogenic malignancy and tuberculosis (TB). A Positron Emission Tomography (PET) scan confirmed a fluorodeoxyglucose (FDG) avid left upper lobe cavitating lesion with enlarged FDG avid thoracic lymphadenopathy. Bronchoscopy and Endobronchial Ultrasound (EBUS) were nondiagnostic. He underwent left upper lobectomy with histopathology confirming Pulmonary actinomycosis and was commenced on Amoxicillin treatment. <br/>Discussion(s): Pulmonary actinomycosis is the third most common type of actinomycosis, behind cervicofacial and abdominal, constituting 15% of total cases. It can occur at all ages, but most case series describe a peak incidence in the 4th and 5th decades. Symptoms are non-specific and often mimic those of it's more common differentials as above and so diagnosing this condition early presents a challenge. Basic laboratory tests reflect the non-specific inflammatory nature of the disease. Imaging modalities (CXR, CT, PET) are helpful, but not diagnostic. The gold standard for diagnosis remains histological examination & bacterial culture of lung biopsy specimen. Histopathologic evidence of granulomas containing neutrophils and sulfur granules with Actinomyces colonies are the hallmark of actinomycosis. Recent data suggests it is increasingly possible to avoid unwarranted surgical procedures, by performing bronchoscopic and percutaneous biopsy techniques. These represent the best chance at preventing unnecessary surgery and should be pursued as they can help exclude malignancy. Penicillin remains the drug of choice for Pulmonary actinomycosis and with correct treatment, the prognosis is excellent. However, those with complications may still require surgery. The chief challenge with Pulmonary actinomycosis is identifying it early, because it is rare, and it also mimics diseases like lung cancer and TB often. We were unable to exclude malignancy with pre-surgical diagnostics and so our patient had surgery. However, clinicians should be aware and consider Pulmonary actinomycosis as an important differential when investigating cavitating lung lesions as diagnosing it early could help prevent physical and psychological morbidity, including unwarranted surgery. (Figure Presented).

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