A Case of Actinomycosis in the Rosenmüller's Fossa.

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.