Breast nonmalignant
Fibroepithelial neoplasms
Fibroadenoma

Editor-in-Chief: Debra Zynger, M.D.
Gary Tozbikian, M.D.

Topic Completed: 31 July 2019

Revised: 30 October 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Fibroadenoma of the breast [title] pathology

Gary Tozbikian, M.D.
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Cite this page: Tozbikian G. Fibroadenoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastfibroadenoma.html. Accessed December 11th, 2019.
Definition / general
  • Benign biphasic tumor composed of a proliferation of both glandular epithelial and stromal components of the terminal duct lobular unit
Essential features
  • Most common breast tumor in adolescent and young women
  • Benign biphasic tumor comprised of glandular epithelium and specialized interlobular stroma of the terminal ductal lobular unit (Pathol Annu 1994;29:1)
  • Can show a spectrum of histologic appearances; generally uniform in stromal cellularity and distribution of glandular and stromal elements within a given lesion (an important distinction from phyllodes tumor)
  • Fibroadenomas with hypercellular stroma and prominent intracanalicular pattern can show morphologic overlap with benign phyllodes tumors, especially in needle biopsy specimens
Terminology
  • Fibroadenoma, usual type fibroadenoma, adult type fibroadenoma
  • Myxoid fibroadenoma
  • Juvenile fibroadenoma
  • Complex fibroadenoma
ICD coding
  • ICD-10: D24 - benign neoplasm of breast
Epidemiology
Sites
  • Breast
  • Can occur in axilla accessory breast tissue
Etiology
Clinical features
  • Often presents as painless, firm, mobile, slow growing mass
  • Usually solitary, can be multiple and bilateral
  • Usually less than 3 cm in diameter but may grow to large size (AJR Am J Roentgenol 2008;190:214)
Radiology description
Radiology images

Contributed by Dr. Mark R. Wick:

Mammogram



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Juvenile fibroadenoma

Case reports
Treatment
  • Management depends on patient risk factors and patient preference
  • Conservative management with close clinical followup, especially if concordant radiology findings
  • Local surgical excision, especially if symptomatic
  • If atypia / neoplasia is found within a fibroadenoma, the surgical and systemic therapeutic management is specific and appropriate to the primary atypical / neoplastic lesion
Gross description
  • Firm, well circumscribed, ovoid mass with bosselated surface, lobulations bulge above the cut surface, slit-like spaces
  • May have mucoid or fibrotic appearance; can be calcified
Gross images

Contributed by Gary Tozbikian, M.D.

Fibroadenoma

Microscopic (histologic) description
  • Well circumscribed, unencapsulated
  • Biphasic tumor, proliferation of both glandular and stromal elements
  • Glandular component
    • Two recognized growth patterns (of no clinical significance, both patterns may occur within a single lesion)
      • Intracanalicular: glands are compressed into linear branching structures by proliferating stroma
      • Pericanalicular: glands retain open lumens but are separated by expanded stroma
    • Glandular elements have intact myoepithelial cell layer
    • Often associated usual type ductal hyperplasia, apocrine metaplasia, cyst formation or squamous metaplasia
    • Rare mitotic activity can be observed in the glandular component, has no clinical significance
  • Stromal component
    • Generally uniform cellularity within a given lesion
    • Collagen and bland spindle shaped stromal cells with ovoid or elongated nuclei
    • Usually no mitotic activity; rare mitotic activity may be present in young or pregnant patients (Breast J 2017;23:182)
    • No stromal atypia
    • Stroma may show myxoid change or hyalinization
    • May show multinucleated giants cells (Am J Surg Pathol 1986;10:823, Arch Pathol Lab Med 1994;118:912)
    • Rarely benign heterologous stromal elements (adipose, smooth muscle, osteochondroid metaplasia)
    • Fibroadenomas may be involved by mammary neoplasia (e.g. invasive breast carcinoma, ductal carcinoma in situ, lobular carcinoma in situ) and atypical epithelial proliferations (e.g. atypical ductal hyperplasia, atypical lobular hyperplasia) of ten as a result of spread from an adjacent lesion
  • Variants
    • Myxoid fibroadenoma
      • Similar structure but with prominent myxoid stromal change composed of abundant pale, blue-gray extracellular matrix material
    • Complex fibroadenoma
      • Cysts > 3 mm, sclerosing adenosis, epithelial microcalcifications or papillary apocrine metaplasia (N Engl J Med 1994;331:10)
    • Cellular fibroadenoma
      • Diffuse stromal hypercellularity
    • Juvenile fibroadenoma
      • Increased stromal cellularity
      • Increased epithelial hyperplasia with gynecomastoid-like micropapillary projections
      • Fascicular stromal arrangement
      • Pericanalicular growth pattern
      • May show rapid growth and large size (Am J Surg Pathol 1985;9:730)
Microscopic (histologic) images

Contributed by Gary Tozbikian, M.D.

Fibroadenoma

Complex fibroadenoma


Myxoid fibroadenoma

Juvenile fibroadenoma


Cellular fibroadenoma


Fibroadenoma with ADH


Fibroadenoma with ALH



Contributed by Debra Zynger, M.D.

Multinucleated stromal cells

Cytology description
Cytology images

Images hosted on other servers:

Diff-Quik

PAP

Clusters of ductal
and myoepithelial
cells within myxoid
stroma

Negative stains
Videos

Fibroadenoma

Sample pathology report
  • Breast, right, 2:00 Zone 2, ultrasound guided core biopsy:
    • Fibroadenoma
Differential diagnosis
Board review question #1
A 13 year old girl presents with a firm, palpable 3.5 cm breast mass. She undergoes an ultrasound guided biopsy and subsequent local excision showing a fibroepithelial lesion with circumscribed borders, uniformly increased stromal cellularity, glandular proliferation with pericanalicular growth pattern and prominent gynecomastoid-like usual type ductal hyperplasia. Rare mitotic activity (< 1/10 hpf) is identified. Stromal cytologic atypia is not present. What is the correct diagnosis?


  1. Fibroadenoma
  2. Juvenile fibroadenoma
  3. Myxoid fibroadenoma
  4. Phyllodes tumor (benign)
  5. Phyllodes tumor (borderline)
Board review answer #1
B. The clinical presentation and histologic features are characteristic of a juvenile fibroadenoma.

Reference: Breast nonmalignant - Fibroadenoma

Comment here
Board review question #2
A 25 year old woman presents with a 3 cm breast mass. An ultrasound guided biopsy shows a fibroepithelial lesion. Which histologic feature is consistent with a diagnosis of fibroadenoma?

  1. Circumscribed borders
  2. Marked stromal cytologic atypia
  3. Stromal condensation around glandular structures
  4. Stromal mitotic activity (7 - 8/10 hpf)
  5. Stromal overgrowth
Board review answer #2
A. Fibroadenomas generally show noninfiltrative, circumscribed borders. The histologic features in answer choices A, B, C and E are observed in phyllodes tumor.

Reference: Breast nonmalignant - Fibroadenoma

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