Abstract
Granulomatous mastitis is a rare benign disease of the breast. We occasionally encounter case reports of granulomatous mastitis that was pathologically diagnosed after operation with a diagnosis of breast cancer. This paper deals with our experience with a case of granulomatous mastitis caused by an infection with Corynebacterium tuberculostearicum (C. tuberculostearicum). The case involved a woman in her fifties, who presented to our hospital because of a left breast tumor with pain. On palpation, an elastic hard and well-movable tumor 40 mm in diameter was felt in the left C area. MMG, US, and MRI strongly suggested breast cancer, and a fine needle biopsy cytology was performed. Histological findings showed infiltration of inflammatory cells mainly composed of neutrophils, but malignant cells were absent. Granulomatous mastitis was suspected, and the punctured content of the tumor was submitted to the laboratory section for cultivation. Antimicrobial drugs were then administered. The culture yielded C. tuberculostearium. The tumor diameter decreased in 4 weeks after the administration. At present when eight months have elapsed after the diagnosis, the patient is doing well without aggravation.
