Tonsillar actinomycosis mimicking relapse of diffuse large B-cell non-Hodgkin lymphoma

We describe a case of tonsillar actinomycosis mimicking relapse of diffuse large B-cell non-Hodgkin lymphoma. Actinomycosis infection is a rare disease, clinical progression it's usually gradual and diagnoses process it's challenging. This report outlines the case of a 63-year-old woman, diagnosed with lymphoma in the right tonsil three years ago, actually in complete remission. During follow-up, there was a slight increase in lactate dehydrogenase (LDH) evaluation. Due to the possibility of a relapse of lymphoma, positron emission tomography-computed tomography (PET-CT) was performed, detecting increased activity in the left oropharynx, which appeared to be thicker in the exam. The patient was submitted to surgical excision of the lesion, with a histological diagnosis of left tonsillar actinomycosis. The genus Actinomyces is composed of non-acid-fast, anaerobic or microaerophilic, commensal bacteria of the oropharynx and the respiratory and digestive tracts. The cervicofacial form is the most common. Surgical excision is frequently essential for a definitive diagnosis. Although uncommon, it is important to include this disease in the differential diagnosis when a tumor-like mass is detected in the cervicofacial region.