Actinomycosis is an infrequent infectious disease caused by Actinomyces species. Actinomycoses in the nasopharynx are extremely rare, especially in the Rosenmüller's fossa. This report presents a case of actinomycosis in the Rosenmüller's fossa. A 75-year-old woman presented with a 6-month history of bloody sputum. A grayish-white caseous tissue was found in the right Rosenmüller's fossa after retracting the torus tubarius. Magnetic resonance imaging showed a well-defined lesion with low-signal intensity on T1- and T2-weighted images; small low-signal areas were interspersed inside. The lesion was removed under an endoscope. Histopathological examination revealed eosinophilic, club-shaped structures surrounding a hematoxylophilic center, leading to the diagnosis of actinomycosis. The symptoms improved after 3 months of amoxicillin administration but recurred quickly. After 6 months of amoxicillin administration, the bloody sputum disappeared, and local and imaging findings were normal.
Keywords: MRI; actinomyces; histopathological examination.