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Idiopathic granulomatous mastitis: a 5-year retrospective review of cases in a tertiary centre in Dublin, Ireland
  1. Elaine Houlihan1,
  2. Katherine Ryan2,
  3. Jennifer Mannion3,
  4. Grace Hennessy2,
  5. Barbara Dunne2,
  6. Elizabeth Connolly3,
  7. Brian O'Connell1
  1. 1Microbiology Department, St James's Hospital, Dublin, Ireland
  2. 2Department of Histopathology, St James's Hospital, Dublin, Ireland
  3. 3Breast/General Surgery Department, St James's Hospital, Dublin, Ireland
  1. Correspondence to Dr Katherine Ryan, Department of Histopathology, St James's Hospital, Dublin, D08 NHY1, Ireland; Ktryan2{at}


Aims Idiopathic granulomatous mastitis (IGM) is a rare, benign, inflammatory breast disorder of unknown aetiology usually affecting women of reproductive age. It classically presents as a unilateral painful breast mass. It is frequently mistaken for carcinoma or other inflammatory breast diseases. Diagnostic investigations include clinical examination, appropriate imaging and tissue sampling. A link between IGM and infection with the Corynebacterium species in particular Corynebacterium kroppenstedtii has been described.

Methods A retrospective single-centre cohort study was conducted over a 5-year period (2017–2022); all cases of IGM were identified.

Results Forty-one patients were diagnosed with IGM. Breast lump was the most common presenting complaint (n=29). The average age was 45 years. Eighteen patients had samples sent for culture and sensitivity, 11 of which had positive microbiology results indicative of Corynebacterium spp infection.

An 82% resolution rate (27 of 33) was recorded in those who received either a short-antibiotic course or none at all. Eight patients reported persistent disease at 3 months, five of which had evidence of Corynebacterium spp.

Discussion This 5-year review highlights the impact of IGM in a tertiary centre in Dublin, Ireland. Although no treatment guidelines exist, options include antibiotics, immunomodulators and surgery. Due to risk of fistulae and unfavourable cosmetic outcomes, surgery should be reserved for refractory IGM. We suspect that there may be a subset of patients where prolonged antibiotic therapy should be considered. Defining this subgroup requires further study, but likely includes those with cystic neutrophilic granulomatous mastitis, relapsing disease and in whom Corynebacterium spp is recovered.

  • Corynebacterium
  • Breast Diseases

Data availability statement

Data are available on reasonable request.

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Data availability statement

Data are available on reasonable request.

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  • Handling editor Runjan Chetty.

  • Contributors To whom it concerns, this was a collaborative research project between three seperate departments in St. James’s Hospital, Dublin, namely the Histopathology department, the Microbiology department and the department of General/breast surgery. EH, KR and JM are joint first authors. All contributed equally to the project, including data collection and interpretation, analysis and coordinating the draft of the manuscript. GH was also involved in data collection and coordinating the draft manuscript. BD, EC and BO'C conceived the study, participated in the design of the overall study and supervised the study. All authors read and approved the final manuscript. Kind regards KR. KR is responsible for the overall content as the guarantor.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.