Breast
Inflammatory
Acute mastitis / abscess

Editorial Board Member: Julie M. Jorns, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Kristen E. Muller, D.O.

Topic Completed: 11 January 2021

Minor changes: 11 January 2021

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PubMed Search: Acute mastitis breast abscess

Kristen E. Muller, D.O.
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Cite this page: Muller, KE. Acute mastitis / abscess. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastacutemastitis.html. Accessed April 16th, 2021.
Definition / general
  • Infection or inflammation of breast tissue, usually bacterial, often seen in association with lactation
  • If untreated, may form abscess and fistulous tracts
Essential features
  • Infection or inflammation of breast tissue, usually bacterial, often seen in association with lactation
  • If untreated, may form abscess and fistulous tracts
  • Staphylococcus aureus most common organism
  • Microscopic examination reveals a mixed dense inflammatory infiltrate, predominantly neutrophils, in breast tissue
Terminology
  • Puerperal mastitis
ICD coding
  • ICD-10:
    • N61.0 - mastitis without abscess
    • N61.1 - abscess of the breast and nipple
    • O91.1 - abscess of the breast associated with pregnancy, the puerperium and lactation
    • O91.211 - nonpurulent mastitis associated with pregnancy, first trimester
    • O91.22 - nonpurulent mastitis associated with the puerperium
  • ICD-11:
    • GB21.Z - inflammatory disorders of breast, unspecified
    • GB21.Y - other specified inflammatory disorders of breast
    • JB45.1 - nonpurulent mastitis associated with childbirth
    • JB45.0 - abscess of breast associated with childbirth
Epidemiology
Sites
  • Subareolar (nonpuerperal)
Pathophysiology
Etiology
Clinical features
  • Erythema, swelling, firmness, breast pain, fever, malaise, decreased milk outflow
  • Abscess: well circumscribed fluctuant mass in addition to above features
  • African Americans may have higher risk of abscess formation (World J Surg 2009;33:2582)
  • Obesity (BMI > 30) and smoking risk factors for abscess (World J Surg 2009;33:2582)
  • Zuska disease (periductal mastitis): clinical scenario of recurring subareolar abscesses and sinus formation (Am J Surg 1951;81:312)
Diagnosis
  • Based on history and clinical findings
  • Ultrasound preferred imagining modality (Radiol Bras 2020;53:405)
  • Biopsy may be warranted for suspected abscess, atypical presentation, recurrent infection or treatment failure; Gram stain and culture (aerobic and anaerobic) with sensitivities to guide antibiotic selection (rarely needed)
  • FNA can be used to drain (Am Fam Physician 2008;78:727)
Radiology description
  • Ultrasound (preferred modality): abscess shows hypoechoic lesion of purulent material, well circumscribed, macrolobulated, irregular or ill defined with septa and thick echogenic rim (Radiographics 2011;31:1683, Radiographics 2007;27 Suppl 1:S101)
  • Mammography of limited value due to nonspecific findings
Radiology images

Contributed by Kristen E. Muller, D.O.
Ultrasound hypoechoic process

Ultrasound hypoechoic process

Ultrasound irregular fluid collection

Ultrasound irregular fluid collection

Prognostic factors
  • Recurrent breast abscesses are more likely to be smokers and have mixed bacterial and anaerobic infections (World J Surg 2009;33:2582)
Case reports
Treatment
Clinical images

Images hosted on other servers:

Mastitis and breast abscess

Lactational abscess

Gross description
  • Excisions rare; specimens usually from incision and drainage procedures and typically received in fragments
Microscopic (histologic) description
  • Mixed dense inflammatory infiltrate, predominantly neutrophils, in breast tissue
  • May obscure underlying normal breast tissue
  • Tissue necrosis may be present
  • Gram stain for microorganisms may reveal bacterial forms (gram positive cocci) associated with neutrophilic infiltrate
  • Granulation tissue and chronic inflammation with resolution
  • Lymphocytes, giant cells and granulomas are not typical (J Pathol Transl Med 2015;49:279)
Microscopic (histologic) images

Contributed by Kristen E. Muller, D.O.
Acute mastitis and abscess Acute mastitis and abscess

Acute mastitis and abscess

Lobular inflammation

Lobular inflammation

Dense inflammatory infiltrate

Dense inflammatory infiltrate

Dense neutrophilic infiltrate

Dense neutrophilic infiltrate

Virtual slides

Images hosted on other servers:

Breast abscess and necrosis

Cytology description
Positive stains
  • Gram stain may highlight Gram positive bacterial forms
Sample pathology report
  • Right breast, core needle biopsy:
    • Breast tissue with abundant acute inflammation and bacterial forms identified on Gram stain (see comment)
    • Comment: The histologic findings are compatible with acute mastitis and abscess formation in the appropriate clinical context. Clinical correlation and correlation with microbiology studies (if performed) is recommended.
Differential diagnosis
  • Squamous metaplasia of lactiferous ducts (SMOLD):
    • Subareolar location
    • Lactiferous ducts with squamous metaplasia
    • Multinucleated giant cells associated with keratin debris
    • Strong association with smoking
  • Fat necrosis:
    • Infarcted adipocytes, lipid laden macrophages, foreign body giant cell reaction
    • Initially acute inflammatory infiltrate may be present, chronic inflammation predominates in older lesions
    • History of surgery, prior biopsy, radiation, trauma
  • Idiopathic granulomatous mastitis:
    • Granulomatous inflammation (lymphocytes, plasma cells, histiocytes, multinucleated giant cells)
    • Lobulocentric pattern, may obliterate lobules
    • May have neutrophils forming microabscesses surrounding empty microcysts; features overlap with cystic neutrophilic granulomatous mastitis, which may have gram positive bacilli within microcysts (Corynebacterium)
  • Duct ectasia:
    • Foamy histiocytes within lumen and within wall and epithelium of ducts, periductal fibrosis
    • Inflammatory cells typically chronic; acute inflammatory infiltrate rarely present
Board review style question #1

What is the most appropriate diagnosis for this breast biopsy from a 32 year old postpartum woman?

  1. Acute mastitis
  2. Duct ectasia
  3. Fat necrosis
  4. Idiopathic granulomatous mastitis
  5. Invasive lobular carcinoma
Board review style answer #1
A. Acute mastitis

Comment Here

Reference: Acute mastitis / abscess
Board review style question #2

Which of the follow is true regarding acute mastitis?

  1. Abscess may form as a complication if left untreated
  2. Acute mastitis typically occurs in postmenopausal women
  3. Granulomas are common
  4. Most common organism isolated is Streptococcus species
Board review style answer #2
A. Abscess may form as a complication if left untreated

Comment Here

Reference: Acute mastitis / abscess
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