Breast

Fibrocystic changes

Microcysts


Editorial Board Members: Julie M. Jorns, M.D., Gary Tozbikian, M.D.
Kristen E. Muller, D.O.

Topic Completed: 19 April 2021

Minor changes: 14 May 2021

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PubMed Search: Breast [title] Microcysts

Kristen E. Muller, D.O.
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Cite this page: Muller KE. Microcysts. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastcysts.html. Accessed October 21st, 2021.
Definition / general
  • Round to ovoid fluid filled structures of variable size lined by bland epithelium, part of nonproliferative fibrocystic changes
Essential features
  • Very common nonproliferative fibrocystic change
  • Round to ovoid fluid filled cysts lined by flat, cuboidal or columnar cells that may be attenuated and denuded
  • Cysts alone do not increase risk of breast cancer
Terminology
  • Blue dome cysts: based on gross appearance
  • Type 1 cysts:
    • Na/K ratio of 3 or less: increased breast cancer risk; associated with higher levels of estrogen, melatonin, epidermal growth factor and DHEA-S and lower levels of TGF-B2 than type 2 cysts (Breast Cancer Res Treat 2007;103:331)
  • Type 2 cysts:
    • Na/K above 3: reduced breast cancer risk, although patients may have both types of cysts and type 2 cysts can be associated with cancer (Breast 2005;14:37)
  • Microcysts: seen during imaging or microscopic exam; not palpable
  • Macro or gross cysts: large enough to be palpated

Note:
  • Type 1 and type 2 terminology is not commonly used
ICD coding
  • ICD-10:
    • N60.0 - solitary cyst of breast
    • N60.19 - diffuse cystic mastopathy of unspecified breast
  • ICD-11: GB20.0 - fibrocystic change
Epidemiology
  • Most common nonproliferative change in breast along with metaplastic changes
  • Any age
  • 20 - 25% of palpable breast abnormalities that underwent fine needle aspiration were simple cysts (Cancer 2001;93:263)
  • Prevalence estimated between 50 - 90% (Breast Cancer Res Treat 2006;97:115)
Sites
  • Usually multifocal and bilateral
Pathophysiology
  • Arises in the terminal ductal lobular unit (TDLU) → dilation and coalescence of lobular acini
  • Gross cysts defined by Haagensen are palpable (Cancer 1989;63:2156)
Etiology
  • Unknown
Clinical features
  • Large cysts may present as a palpable mass
Diagnosis
  • Fine needle aspiration:
    • Mass disappears after aspiration and the fluid is nonbloody, yellow or green and serous, no further workup necessary (Can Fam Physician 2012;58:1240)
    • Further workup starting with imaging required after aspiration if no fluid, bloody or tenacious fluid or mass persists (Am Fam Physician 2003;68:1983)
    • Bloody or cloudy or turbid fluid should be sent for cytopathology review
Radiology description
Radiology images

Contributed by Kristen E. Muller, D.O.
Hypoechoic mass, ultrasound

Hypoechoic mass, ultrasound

Circumscribed mass, mammogram

Circumscribed mass, mammogram

Prognostic factors
Case reports
Treatment
  • Aspiration / decompression if symptomatic or for diagnostic purposes (See Diagnosis section)
Gross description
  • Variable size, usually visible grossly, contains clear, straw colored or brown fluid
  • Larger intact cysts may appear blue (blue domed cyst) (Breast Cancer Res Treat 2006;97:115)
Gross images

Contributed by Kristen E. Muller, D.O. and AFIP images
Numerous grossly visible cysts

Numerous grossly visible cysts

Large hemorrhagic cysts

Large hemorrhagic cysts



Images hosted on other servers:

Unopened cyst

Extensive cystic disease

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Kristen E. Muller, D.O.
Simple epithelial lining

Simple epithelial lining

Flattened epithelial lining

Flattened epithelial lining

Denuded epithelial lining

Denuded epithelial lining

Cysts, columnar cell change Cysts, columnar cell change Cysts, columnar cell change

Cysts, columnar cell change


Surrounding fibrosis and inflammation Surrounding fibrosis and inflammation

Surrounding fibrosis and inflammation

Ruptured cyst Ruptured cyst

Ruptured cyst

Cluster of microcysts

Cluster of microcysts

Cytology description
  • Hypocellular aspirate, macrophages with other inflammatory cells, with or without few clusters of benign ductal epithelial and myoepithelial cells (Patholog Res Int 2011;2011:547580)
  • Prior rupture of the cyst may result in turbid or milky fluid, degenerated cells and debris in an abundant background of inflammatory cells (Patholog Res Int 2011;2011:547580)
Cytology images

Contributed by Kristen E. Muller, D.O.
Predominantly debris, cell block

Predominantly debris, cell block

Hypocellular specimen, LBP

Hypocellular specimen, LBP

Sample pathology report
  • Left breast, 2 o’clock, 1 cm from nipple, core needle biopsy:
    • Benign breast tissue with fragments of cyst wall with surrounding fibrosis and chronic inflammation
Differential diagnosis
Board review style question #1

The findings pictured are from a 38 year old woman with a cystic breast mass. What is the diagnosis?

  1. Atypical ductal hyperplasia
  2. Cysts
  3. Duct ectasia
  4. Flat epithelial atypia
  5. Lymphocytic mastitis
Board review style answer #1
B. Cysts

Comment Here

Reference: Microcysts
Board review style question #2

The findings pictured are from a 67 year old woman with a palpable breast mass. Ultrasound showed a complex cystic and solid mass. What is the diagnosis?

  1. Duct ectasia
  2. Ductal carcinoma in situ
  3. Granulomatous mastitis
  4. Ruptured cyst wall
Board review style answer #2
D. Ruptured cyst wall

Comment Here

Reference: Microcysts
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