Breast
Infectious
Cystic neutrophilic granulomatous mastitis


Topic Completed: 24 September 2020

Minor changes: 24 September 2020

Copyright: 2018-2020, PathologyOutlines.com, Inc.

PubMed Search: CNGM

Gulisa Turashvili, M.D., Ph.D.
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Cite this page: Wu JM, Turashvili G. Cystic neutrophilic granulomatous mastitis . PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastcysticgranulomatousmastitis.html. Accessed October 20th, 2020.
Definition / general
  • Inflammatory process of the breast usually due to Corynebacterium species
Essential features
  • Most patients are women, parous or currently pregnant
  • Characteristic morphologic features include granulomas comprised of epithelioid histiocytes and giant cells with central lipid vacuoles containing gram positive bacteria and rimmed by neutrophils
  • Association with Corynebacterium species, especially Corynebacterium kroppenstedtii, although microbiologic evidence can be difficult to obtain
  • Prolonged antibiotic therapy required for complete resolution
Terminology
  • Not recommended: granulomatous mastitis, idiopathic granulomatous mastitis, granulomatous lobular mastitis, idiopathic lobular granulomatous mastitis
Epidemiology
  • Rare, with at least 141 cases reported since 2002 (J Clin Pathol 2020;73:445)
  • Female patients, parous or currently pregnant
  • Mean age 35 years (range 19 - 57)
Sites
Etiology
Clinical features
  • Most commonly painful breast mass, nipple inversion or sinus formation (J Clin Pathol 2020;73:445)
  • Nipple discharge, skin erythema and abscess
  • Fever and leukocytosis
  • Axillary lymphadenopathy
Diagnosis
  • Microscopic examination and Gram stain with or without microbiologic culture
Laboratory
Radiology description
Radiology images

Images hosted on other servers:

Palpable breast mass

Prognostic factors
  • Prolonged (weeks to months) antibiotic therapy required for complete resolution
  • May recur with inadequate therapy
Case reports
Treatment
  • Observation
  • Antibiotics:
    • Empirical antimicrobial therapy may be started prior to histologic diagnosis
    • Lipophilic antibiotics such as doxycycline, trimethoprim sulfamethoxazole, clarithromycin and rifampicin may be more effective (J Clin Microbiol 2015;53:2895)
    • Antibiotic susceptibility test should be performed
  • Steroids
  • Surgery including incision and drainage, excision and even mastectomy
  • Combination of the above therapies
Gross description
Microscopic (histologic) description
  • Presence of 2 - 3 of the following features (J Clin Pathol 2020;73:445):
    • Lobulocentric mixed inflammatory infiltrate composed of lymphocytes, neutrophils and scattered multinucleated giant cells
    • Round to oval cystic spaces (lipid vacuoles) rimmed by neutrophils (microabscesses)
    • Nonnecrotizing granulomas
  • Combined with either:
    • Presence of coryneform gram positive bacilli (rod shaped bacteria arranged in V shaped forms or palisades like Chinese characters) within lipid vacuoles or
    • Positive Corynebacteria culture or molecular testing
Microscopic (histologic) images

Contributed by Jessie M. Wu, M.B.Ch.B. and Gulisa Turashvili, M.D., Ph.D.
Mixed inflammation Mixed inflammation

Mixed inflammation

Lipid vacuoles

Lipid vacuoles

Gram stain

Gram stain



Contributed by Ankur Sangoi, M.D. (Case #462)
Mixed inflammation Mixed inflammation

Mixed inflammation

Lipid vacuoles Lipid vacuoles

Lipid vacuoles

Gram stain Gram stain

Gram stain

Cytology description
  • Cytologic diagnosis may be difficult
  • Limited by significant cytomorphologic overlap with granulomatous mastitis and other inflammatory breast lesions
  • Features suggestive of cystic neutrophilic granulomatous mastitis on ThinPrep include cystic spaces, inflammatory cells such as neutrophils with aggregates of epithelioid histiocytes, multinucleated giant cells, lymphocytes and plasma cells and lack of necrosis (Diagn Cytopathol 2018;46:966)
Positive stains
  • CD68: positive in histiocytes
  • Gram positive coryneform bacteria within lipid vacuoles:
    • Rod shaped bacteria arranged in V shaped forms or palisades like Chinese characters
    • Bacteria may not be identified in all lipid vacuoles
    • Thick section Gram stain performed at 6 µm (vs 4 µm) improves both detection rate and ease of identification of gram positive bacilli (Am J Clin Pathol 2020;153:593)
Negative stains
Molecular / cytogenetics description
Sample pathology report
  • Right breast, core biopsy:
    • Cystic neutrophilic granulomatous mastitis (see comment)
    • Comment: A tissue gram stain highlights gram positive bacilli, supporting the diagnosis. Controls are appropriate.
    • Microscopic description (optional): Sections show a perilobular mixed inflammatory infiltrate composed of central lipid vacuoles rimmed by neutrophils and an outer cuff of epithelioid histiocytes. Some of the lipid vacuoles contain sparse, rod shaped, gram positive bacilli. The surrounding inflammatory infiltrate contains multinucleated giant cells, lymphocytes and neutrophils. The morphology combined with the presence of gram positive bacilli on Gram stain is consistent with cystic neutrophilic granulomatous mastitis.
Differential diagnosis
Board review style question #1

A 35 year old woman presents with a right breast mass. Core biopsy shows empty appearing cystic spaces rimmed by neutrophils and an outer cuff of epithelioid histiocytes. Some vacuoles contain sparse, rod shaped bacilli. Which organism is most commonly associated with this type of granulomatous mastitis?

  1. Corynebacterium diphtheriae
  2. Corynebacterium kroppenstedtii
  3. Mycobacterium tuberculosis
  4. Staphylococcus aureus
  5. Staphylococcus epidermidis
Board review answer #1
B. Corynebacterium kroppenstedtii. Cystic neutrophilic granulomatous mastitis is most commonly associated with Corynebacterium kroppenstedtii.

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Reference: Cystic neutrophilic granulomatous mastitis
Board review style question #2
Cystic neutrophilic granulomatous mastitis most commonly affects which of the following patient population?

  1. Female smokers
  2. Parous women
  3. Postmenopausal women
  4. Women living in endemic areas of tuberculosis
  5. Women with a history of Corynebacterium diphtheriae infection
Board review answer #2
B. Parous women. Cystic neutrophilic granulomatous mastitis most commonly affects women who are currently pregnant or have been pregnant.

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Reference: Cystic neutrophilic granulomatous mastitis
Board review style question #3
Which of the following statements is true regarding cystic neutrophilic granulomatous mastitis?

  1. Diagnosis may require matrix assisted laser desorption / ionization time of flight mass spectrometry
  2. Gram positive bacilli are identified in nearly all cases
  3. Resolution typically takes days
  4. Usually presents as a painless palpable mass in postmenopausal women
Board review answer #3
A. Diagnosis may require matrix assisted laser desorption / ionization time of flight mass spectrometry. Diagnosis of cystic neutrophilic granulomatous mastitis may require culture, 16S rRNA gene sequencing or matrix assisted laser desorption / ionization time of flight mass spectrometry.

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Reference: Cystic neutrophilic granulomatous mastitis
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