Corynebacterium kroppenstedtii in granulomatous mastitis: Analysis of formalin-fixed, paraffin-embedded biopsy specimens by immunostaining using low-specificity bacterial antisera and real-time polymerase chain reaction.

Granulomatous mastitis (GM) is a rare inflammatory disease of the post-lactation breast, clinically mimicking breast cancer. GM is microscopically characterized by formation of epithelioid granulomas and abscess (suppurative granulomas) with lipid droplet-centered inflammation. Corynebacterium kroppenstedtii (Ck) is known as a causative bacterium of GM, and identification of Ck infection within the lesion should thus be essential for confirming the diagnosis.

Fine needle aspiration cytology of nodular fasciitis of the breast.

We report a case of nodular fasciitis (NF) of the breast, which was cytologically diagnosed as a spindle cell proliferation with undetermined malignant potential. Owing to small size of the lesion (5.9 × 3.