Actinomycotic ulcer of the oral mucosa: an unusual presentation of oral actinomycosis.

Although the oral mucosa is often the site of entry of actinomyces into the deeper tissues, actinomycosis in the oral mucosa is extremely rare. Actinomycotic lesions are usually described as either single or multiple abscesses or indurated masses with hard fibrous walls and soft central loculations. Actinomyces israelii is the principal cause of human actinomycosis. We present a rare case of actinomycosis caused by Actinomyces odontolyticus; it presented primarily as a long-standing ulcer of the oral mucosa mimicking a squamous cell carcinoma.