A rare case of primary actinomycosis of the breast caused by Actinomyces viscosus: diagnosis by fine-needle aspiration cytology under ultrasound guidance.

We report the case of a 27-year-old woman with primary actinomycosis of the breast. Diagnosis was established by culture examination of specimen recovered by fine-needle aspiration cytology (FNAC) under ultrasound guidance. To our knowledge, this is the first description in the literature of a case of primary actinomycosis of the breast caused by Actinomyces viscosus. Twenty-nine previous cases of primary actinomycosis of the breast have been published, but these were caused by the more common species Actinomyces israelii. Targeted antibiotic therapy did not ameliorate the condition, thus drainage and excision of the mass were carried out. No other medical therapy was administered. Six years after surgery, no recurrence has been observed on both ultrasonographic and mammographic examinations.