Breast
Fibroepithelial tumors
Phyllodes tumor


Minor changes: 29 September 2020

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PubMed Search: Phyllodes tumor of the breast[TI] full text[SB] pathology

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Cite this page: Li JJX, Tse GM. Phyllodes tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastphyllodesgeneral.html. Accessed October 26th, 2020.
Definition / general
  • Biphasic fibroepithelial neoplasm with leaf-like epithelial (phyllodal) pattern and stromal proliferation
Essential features
  • Biphasic fibroepithelial lesion characterized by leaf-like phyllodal epithelial pattern
  • Graded and prognosticated by histologic changes of the stromal proliferation
  • Epithelial component is benign in phyllodes tumor
Terminology
  • Phyllodes tumor
  • Cystosarcoma phyllodes (the use of this term is discouraged)
ICD coding
  • Phyllodes tumor
    • ICD-O: 9020/1 - Phyllodes tumor, NOS
  • Benign phyllodes tumor
    • ICD-O: 9020/0 - Phyllodes tumor, benign
    • ICD-10: D24 - Benign neoplasm of breast
    • ICD-11: 2F30.3 - Benign phyllodes tumor of breast
    • ICD-11: XH50P7 - Phyllodes tumor, benign
  • Borderline phyllodes tumor
    • ICD-O: 9020/1 - Phyllodes tumor, borderline
    • ICD-11: 2F75 - Neoplasms of uncertain behavior of breast
    • ICD-11: XH5NK4 - Phyllodes tumor, borderline
  • Malignant phyllodes tumor
    • ICD-O: 9020/3 - Phyllodes tumor, malignant
    • ICD-10: D48.6 - Cystosarcoma phyllodes (the use of this term is discouraged)
    • ICD-11: 2C63 - Malignant phyllodes tumor of breast
    • ICD-11: XH8HJ7 - Phyllodes tumor, malignant
Epidemiology
Sites
Pathophysiology
Etiology
Clinical features
Diagnosis
Radiology description
  • Oval and lobulated lesions
  • Hypoechoic on ultrasound
  • Microcalcifications rare
Radiology images

Contributed by Mark R. Wick, M.D.
Mammogram

Mammogram, benign

Prognostic factors
Case reports
Treatment
Clinical images

Images hosted on other servers:
Large tumor

Large tumor

Malignant tumor

Malignant tumor

Swollen breast

Swollen breast

Gross description
  • Rounded, shelled out borders
    • Infiltrative in malignant and less commonly borderline phyllodes tumor
  • Whorled, bosselated cut surface in a leaf-like pattern
  • Skin ulceration, hemorrhage and cystic changes in large lesions (Int J Surg Case Rep 2020;67:114)
    • Ulceration and hemorrhage do not indicate malignant behavior per se
    • Infarcted or very large benign phyllodes tumor can also show necrosis
Gross images

Contributed by Mark R. Wick, M.D.

Benign phyllodes tumor



Images hosted on other servers:

Large, well circumscribed tumor, benign

Malignant

Microscopic (histologic) description
  • Leaf-like (phyllodal) epithelial pattern formed by an exaggerated intracanalicular pattern
  • Subepithelial condensation with increased stromal cellularity adjacent to epithelium
  • Graded into benign, borderline and malignant histologic grades


    Benign Borderline Malignant
    Stromal atypia Mild Moderate Marked
    Stromal cellularity Mildly increased, can be focal Moderately increased, can be focal Markedly and diffusely increased
    Stromal overgrowth* Absent Absent or very focal Present
    Mitotic count < 5/10 HPF or < 2.5/mm² 5 - 9/10 HPF or 2.5 - < 5/mm² ≥ 10/10 HPF or ≥ 5/mm²
    Tumor border Well defined Well defined or focally permeative Diffusely permeative
    Malignant heterologous elements Absent Absent Presence directly upgrades to malignant category**
      *Defined as absence of epithelial elements containing stroma only in 1 low power field
      **Includes chondrosarcoma, liposarcoma (except well differentiated liposarcoma), osteosarcoma, rhabdomyosarcoma, angiosarcoma and leiomyosarcoma

  • Cystic degeneration, hemorrhage, stromal hyalinization and myxoid change reported
  • Multinucleated stromal giant cells occasionally seen (Pathology 2001;33:153)
    • Can be found in phyllodes tumor of all histologic grades
  • Epithelial elements usually bland
  • Myoepithelial layer is preserved but can be attenuated
Microscopic (histologic) images

Contributed by Joshua J.X. Li, M.B.Ch.B. and Gary M. Tse, M.B.B.S.

Benign phyllodes tumor
Leaf-like epithelial pattern

Leaf-like epithelial pattern

Low stroma to epithelium ratio

Low stroma to epithelium ratio

Rounded borders

Rounded borders

Shelled out tumor

Shelled out tumor

Benign stromal cells

Benign stromal cells



Borderline phyllodes tumor
Phyllodal pattern

Phyllodal pattern

Stromal overgrowth

Stromal overgrowth

Distorted epithelium

Distorted epithelium

Stromal mitosis

Stromal mitosis

Stromal atypia

Stromal atypia



Malignant phyllodes tumor
Infiltrative borders

Infiltrative borders

Marked stromal overgrowth

Marked stromal overgrowth

High stromal cellularity

High stromal cellularity

Stromal atypia

Stromal atypia

Stromal giant cells

Stromal giant cells

Atypical mitosis

Atypical mitosis

Virtual slides

Images hosted on other servers:

Benign phyllodes tumor
Benign phyllodes tumor

Benign phyllodes tumor

Intraductal growth pattern

Intraductal growth pattern


Borderline phyllodes tumor
Borderline phyllodes tumor

Borderline phyllodes tumor

Tumor hemorrhage

Tumor hemorrhage



Malignant phyllodes tumor
Malignant lipomatous element

Malignant lipomatous element

Malignant osteosarcomatous element

Malignant osteosarcomatous element

Extensive stromal overgrowth

Extensive stromal overgrowth

Cytology description
  • Fibromyxoid stromal clumps
    • Reduced epithelial stromal ratio compared with fibroadenomas
    • Higher nuclear atypia and cellularity in phyllodes tumor of higher grades
  • Large wavy and folded epithelial clusters
    • Usually exhibits benign cytomorphology
    • Occasionally, hyperplastic changes with enlarged and vesicular nuclei and small visible nucleoli may be seen
  • Fibroblastic pavements
  • Increased atypia in dispersed cells in phyllodes tumor of higher grades (Cancer Cytopathol 2010;118:33)
  • Multinucleated tumor cells and marked stromal anaplasia reported in malignant phyllodes tumor (Cancer Cytopathol 2010;118:33)
Cytology images

Contributed by Joshua J.X. Li, M.B.Ch.B. and Gary M. Tse, M.B.B.S.

Benign phyllodes tumor
Biphasic pattern

Biphasic pattern

Fibromyxoid stromal clumps

Fibromyxoid stromal clumps

Benign stromal cells

Benign stromal cells


Borderline phyllodes tumor
Increased stroma to epithelium ratio

Increased stroma to epithelium ratio

Stromal cellularity

Stromal cellularity

Stromal atypia

Stromal atypia



Malignant phyllodes tumor
Atypical stromal cells

Atypical stromal cells

Positive stains
Negative stains
Molecular / cytogenetics description
  • Recurrent MED12 and RARA mutations in phyllodes tumors of all grades and fibroadenoma (Nat Genet 2015;47:1341)
    • More frequent in benign phyllodes tumor
  • Mutations in cancer driver genes (NF1, RB1, PIK3CA, EGFR, TP53 and ERBB4) exclusively seen in borderline and malignant phyllodes tumors (Nat Genet 2015;47:1341)
  • TERT promoter mutation more common in borderline phyllodes tumor (Sci Rep 2018;8:3881)
  • Chromosome abnormalities increase with grade (Mod Pathol 2007;20:435)
    • Notably 1q gain and 13q loss
Sample pathology report
  • Left breast, local excision:
    • Benign phyllodes tumor (see comment and synoptic report)
    • Comment: Sections show a stromal proliferation in a leaf-like pattern capped by benign ductal epithelium and intact intervening myoepithelial cell layer. The stromal proliferation is of low cellularity and the stromal cells show mild atypia. Stromal mitosis and stromal overgrowth are not prominent. The tumor is circumscribed.
  • Left breast, wide local excision:
    • Borderline phyllodes tumor (see comment and synoptic report)
    • Comment: Sections show a stromal proliferation featuring areas of leaf-like pattern and stromal expansion with moderate cellularity and stromal atypia. Scattered stromal mitotic figures are noted. The tumor is largely circumscribed with focally infiltrative borders.
  • Left breast, local excision:
    • Malignant phyllodes tumor (see comment and synoptic report)
    • Comment: Sections show a malignant spindle cell proliferation with diffusely increased cellularity and marked stromal atypia. Stromal mitotic figures are frequent. Focal epithelial structures in a leaf-like pattern is noted. Stromal overgrowth is noted with absence of epithelial component in 1 low power field. The tumor shows infiltrative border.
Differential diagnosis
  • Benign phyllodes tumor
    • Fibroadenoma:
      • Shows a combination of pericanalicular and intracanalicular epithelial patterns
      • No phyllodal epithelial pattern
      • Relatively uniform stromal cellularity, no subepithelial condensation
      • Overlap in stromal cellularity and mitosis in cellular and juvenile fibroadenomas
      • No significant stromal expansion
    • Fibromatosis:
  • Borderline / malignant phyllodes tumor
Board review style question #1

A 36 year old woman presents with a self palpated breast mass. Imaging shows a rounded nodule; excision with narrow negative margins was performed. Stromal atypia and mitosis are absent. What is the most suitable follow up management for the patient?

  1. Adjuvant chemotherapy
  2. Hormonal therapy
  3. Local radiotherapy
  4. Lymph node dissection
  5. Observation
Board review answer #1
E. Observation. Benign phyllodes tumor is not associated with mortality or metastasis; additional therapy is not indicated.

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Reference: Phyllodes tumor
Board review style question #2
Which of the following features can be seen in a benign phyllodes tumor?

  1. Diffusely increased stromal cellularity
  2. Focally permeative borders
  3. Presence of concurrent invasive duct carcinoma
  4. Presence of rhabdomyosarcomatous elements
  5. Stromal mitotic count of 8/10 HPF
Board review answer #2
C. Presence of concurrent invasive duct carcinoma. Although prognosis of benign phyllodes tumor may be guided by premalignant or malignant epithelial changes, they are rare and are usually incidental, thus are not incorporated into the routine grading of phyllodes tumor.

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Reference: Phyllodes tumor
Board review style question #3
Which of the following features is diagnostic of malignant phyllodes tumor?

  1. Focus of infiltrative tumor border
  2. Involvement by low grade ductal carcinoma in situ
  3. Multinucleated stromal giant cell
  4. Small focus of osteosarcomatous differentiation
  5. Stromal overgrowth
Board review answer #3
D. Small focus of osteosarcomatous differentiation. Borderline phyllodes tumor allows for, albeit a lesser degree compared to malignant phyllodes tumor, stromal overgrowth and an infiltrative tumor border. Multinucleated stromal giant cells can be seen in all grades of phyllodes tumor and does not impact histologic grading. The epithelial component of phyllodes tumor can show metaplasia, hyperplasia, in situ or invasive malignant changes, which may impact prognosis but does not affect histologic grading. Presence of malignant heterologous differentiation directly upgrades a phyllodes tumor into the malignant category.

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Reference: Phyllodes tumor
Board review style question #4
Which of the following features can be seen in malignant phyllodes tumors but not metaplastic carcinomas?

  1. Bizarre anaplastic tumor cells
  2. Cytokeratin expression
  3. MED12 mutation
  4. p53 expression
  5. Rhabdomyosarcomatous differentiation
Board review answer #4
C. MED12 mutation. MED12 and RARA are frequent mutations in fibroepithelial lesions of the breast and are believed to be involved in the tumorigenesis of fibroepithelial lesions. MED12 and RARA mutations are absent in metaplastic carcinomas (Clin Cancer Res 2017;23:3859). p53 expression and TP53 mutation are detected in both malignant phyllodes tumor and metaplastic carcinomas. Aberrant cytokeratin expression, albeit patchy, can be seen in malignant phyllodes tumor. Bizarre tumor cells and malignant heterologous elements can be seen in both entities.

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Reference: Phyllodes tumor
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