Actinomycosis of the Tongue Mimicking a Benign Tumor: A Case Report With Ultrasonographic and Histopathological Findings.

We report a rare case of actinomycosis arising in the tongue. A female patient in her 70s presented to our department with swelling of the tongue. Despite only minimal mucosal change, a submucosal indurated mass was observed. Contrast-enhanced magnetic resonance imaging revealed a well-circumscribed mass-like lesion within the tongue muscle. Ultrasonography showed punctate hyperechoic foci within a hypoechoic lesion. As there were few signs of infection, a benign tumorous lesion was suspected, and an excisional biopsy was performed. Histopathological examination indicated sulfur granules in the mass, and no neoplastic lesion was observed. The mass was ultimately diagnosed as tongue actinomycosis. Three years after surgery, there was no evidence of recurrence at the wound site. This case highlights the diagnostic difficulty of lingual actinomycosis and suggests that internal punctate hyperechoic foci on ultrasonography may provide a useful clue to the diagnosis.