RESUMO
Actinomycosis is a rare chronic suppurative infectious disease caused by Actinomyces spp. Actinomyces are anaerobic Gram-positive bacteria that colonize the mouth, digestive tract, and genital tract. Thoracic actinomycosis is caused by the aspiration of oropharyngeal materials or the spread of cervicofacial infections. Therefore, poor oral hygiene, smoking, and immunodeficiency are risk factors. Actinomycoses are frequently misdiagnosed as anatomical malignancies and thus assessments of the diseases underlying malignancies are often complicated by the presence of actinomycoses. Here, we report a case of mediastinal actinomycosis presenting with clinical and radiological features of metastatic pancreatic cancer. Clinicians should consider the presence of actinomycosis when cancer patients fail to respond to anti-cancer treatments.