Detection of Corynebacterium kroppenstedtii in Granulomatous Lobular Mastitis Using Real-Time Polymerase Chain Reaction and Sanger Sequencing on Formalin-Fixed, Paraffin-Embedded Tissues.

Context.—: Associations between granulomatous lobular mastitis (GLM) and Corynebacterium kroppenstedtii have been reported since 2002, but large-scale studies to assess the actual prevalence of this bacterium in GLM have not been performed.

Objective.—: To assess the prevalence of C kroppenstedtii in GLM using real-time polymerase chain reaction and Sanger sequencing.

Design.—: We analyzed formalin-fixed, paraffin-embedded tissues from 67 cases of GLM by sequential DNA amplification and sequencing to assess the rate of C kroppenstedtii detection in GLM. A retrospective analysis including patient demographics, history of pregnancy and lactation, clinical signs and symptoms, radiographic findings, histologic pattern, Gram stain results, and microbial cultures was performed on 67 cases of GLM. In addition, 10 cases of nongranulomatous breast abscess were included as controls.

Results.—: C kroppenstedtii 16S rRNA SYBR real-time polymerase chain reaction was positive on formalin-fixed, paraffin-embedded tissues from 46 of 67 (68.7%) GLM cases, while all control cases were negative. Among the positive cases, the majority showed features of cystic neutrophilic granulomatous mastitis.

Conclusions.—: C kroppenstedtii was highly prevalent in GLM cases and was not found to be associated with nongranulomatous breast abscess in our study (P < .001).