Breast

• Lobulocentric granulomatous inflammation
• Diagnosis of exclusion (excluding other causes of granulomatous inflammation)

• Rare
• Most common in parous women, childbearing age
• Frequent in postpartum and breastfeeding women
• Median age in the 30s

• Breast, most often unilateral, rarely bilateral

• Unknown

• Unknown
• Proposed causes or associations: pregnancy, lactation, oral contraceptive pill use, hyperprolactinemia, autoimmunity, infection

• Mimics breast cancer, including inflammatory breast cancer (Breast J 2019;25:1245)
• Palpable breast mass
• Breast pain
• Abscess formation with fistula tract formation
• Nipple retraction
• Peau d'orange
• Rare lymphadenopathy

• Breast core biopsy or surgical excision with histologic examination

• Microbiology studies to exclude infection
• Serologic markers to exclude autoimmune processes
• Endocrine studies

• Nonspecific imaging findings (Radiographics 2018;38:330)
• Mammography: focal asymmetric density (Clin Imaging 2021;69:126)
• Ultrasound: irregular hypoechoic mass with tubular projections (Clin Imaging 2021;69:126)
• MRI: nonmass-like enhancement; ring enhancing lesions (Acta Radiol 2016;57:796, Clin Imaging 2021;69:126)

Images hosted on other servers:

• 33 year old woman with chronic breast wound (Breast J 2020;26:281)
• 36 year old woman with tender breast mass (Int Semin Surg Oncol 2007;4:21)
• 37 year old woman with painless breast mass (J Clin Diagn Res 2017;11:PD14)
• 43 year old woman with tender breast mass and erythema nodosum (JAAD Case Rep 2016;2:125)

Contributed by Nicolas Ajkay, M.D.


Images hosted on other servers:

Contributed by Jonathan Marotti, M.D. and Mary Ann Gimenez Sanders, M.D., Ph.D.

• Cystic neutrophilic granulomatous mastitis (CNGM) (J Clin Pathol 2020;73:445):
  • Small cystic spaces lined by neutrophils with cuff of epithelioid histiocytes
  • Cysts contain rare gram positive bacilli (Corynebacterium)
• Granulomatous mastitis due to infection:
  • Tuberculosis mastitis:
    • Necrotizing granulomas
    • Inflammation affects ducts and lobules
    • Acid fast stain, culture or polymerase chain reaction to identify Mycobacterium
  • Fungal mastitis:
    • GMS, PAS stains to identify fungi
• Foreign body reaction:
  • Foreign body type granulomas and giant cells
  • Presence of foreign material
• Granulomatosis with polyangiitis:
  • Necrotizing vasculitis
  • c-ANCA positive
• Sarcoidosis:
  • Well formed granulomas not confined to the lobules
• Squamous metaplasia of lactiferous ducts (SMOLD):
  • Associated with smoking
  • Keratinizing squamous metaplasia of nipple ducts with foreign body inflammatory response
• IgG4 related sclerosing mastitis (J Clin Pathol 2020 Dec 16 [Epub ahead of print]):
  • Storiform fibrotic process with eosinophils and increased IgG4 positive plasma cells
  • Obliterative phlebitis
  • Granulomas typically absent

A 33 year old woman presents with a painful breast lump concerning for breast cancer. A core biopsy is performed. Which histologic finding is most characteristic of idiopathic granulomatous mastitis?

1. Keratin debris with associated foreign body inflammatory response
2. Large necrotizing granulomas
3. Lobulocentric granulomatous inflammation
4. Microcysts with gram positive bacilli
5. Well formed granulomas within interlobular stroma

C. Lobulocentric granulomatous inflammation. Although not specific, the most characteristic histologic finding of idiopathic granulomatous mastitis is granulomatous inflammation centered on lobules (lobulocentric inflammation). Idiopathic granulomatous mastitis can have overlapping histologic features with cystic neutrophilic granulomatous mastitis (CNGM); however, microcysts with gram positive bacilli (Corynebacterium) are identified in CNGM. Keratin debris with an associated foreign body inflammatory response is usually seen in squamous metaplasia of lactiferous ducts (SMOLD). Large necrotizing granulomas are more typical of an infectious processes, such as mycobacterial infection. The presence of well formed granulomas within the interlobular stroma suggests sarcoidosis.

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Reference: Idiopathic granulomatous mastitis