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Surgical Pathology Criteria
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Phyllodes Tumor of the Breast

Definition

  • Mixed epithelial and stromal/mesenchymal proliferation of breast characterized by increased stromal cellularity and characteristic broad "leaf-like" papillae inserted into cleft-like spaces

Alternate/Historical Names

  • Cystosarcoma phyllodes

Diagnostic Criteria

  • Usually large and grossly circumscribed
  • Fibroepithelial proliferation with broad "leaf-like" papillae inserting into slit-lilke or cleft-like spaces
    • Exaggerated intracanalicular pattern
  • Cellular stroma
    • Periductal stromal condensation may be seen
  • Frankly sarcomatous stroma may be seen in malignant phyllodes tumor
    • Heterologous differentiation may occur in malignant phyllodes tumor
      • Liposarcoma
      • Osteosarcoma
      • Chondrosarcoma
      • Rhabdomyosarcoma
  • Grading determined by presence or absence of atypical stromal features

Kristin C Jensen MD
Richard L Kempson MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: January 10, 2007

Supplemental studies

Immunohistology and Genetic Analysis

  • No diagnostically useful markers currently reported

Differential Diagnosis

Juvenile Fibroadenoma Low Grade Phyllodes Tumor
No leaf-like architecture Prominent leaf-like architecture
No condensation around ducts Stromal condensation around ducts
Does not infiltrate May infiltrate surrounding breast
The histologic border between these two is not always sharp

 

Juvenile Fibroadenoma High Grade Phyllodes Tumor
No stromal atypia Atypical stroma
Stromal mitotic rate < 3/10 hpf Elevated stromal mitotic rate
No stromal overgrowth Stromal overgrowth
Does not infiltrate May infiltrate surrounding breast
Stromal overgrowth defined as at least one low power field (40x total magnification) composed entirely of stroma

Fibroadenoma Low Grade Phyllodes Tumor
Lacks significant stromal hypercellularity Hypercellular stroma is prominent
No stromal overgrowth May have stromal overgrowth
No leaf-like architecture Prominent leaf-like architecture
No condensation around ducts Stromal condensation around ducts
Does not infiltrate May infiltrate surrounding breast
The histologic border between these two is not always sharp

Metaplastic Carcinoma Phyllodes Tumor
Spindled component may be positive for high molecular weight keratin or p63 Stromal component negative for high molecular weight keratin and p63
Epithelial component is malignant Epithelial component is benign
Squamous differentiation may be present No squamous differentiation

Pure Sarcoma of the Breast

  • Very rare
  • The presence of an epithelial component defines phyllodes tumor

 

Fibromatosis

  • Bland spindle cells
  • Stellate configuration
  • Absence of intrinsic epithelial component
    • May entrap normal breast lobules

 

Myofibroblastoma

  • Resembles solitary fibrous tumor
  • Lacks intrinsic epithelial component

Clinical

  • Often rapid growth and large size (>3-4 cm)
  • Local recurrence is common
    • Metastasis is rare

Grading / Staging / Report

Grading

  • Adverse features
    • Stromal overgrowth (> one 40x field without epithelium)
    • High mitotic index (>10 /10 hpf)
    • Sarcomatous stroma (stromal nuclear pleomorphism and atypia)
    • Infiltrative margin
  • Benign
    • No adverse features
    • 20% recurrence rate after local excision
    • 10% recurrence rate after wide excision (at least 1 cm margin)
    • No reported metastases
  • Borderline
    • One or more adverse features but short of definition for malignant (see below)
    • 45% recurrence rate after local excision
    • 30% recurrence rate after wide excision (at least 1 cm margin)
    • No reported metastases
  • Malignant
    • High mitotic index and sarcomatous stroma OR
    • Stroma overgrowth and either high mitotic index or sarcomatous stroma
    • 65% recurrence rate after local excision
    • 35% recurrence rate after wide excision (at least 1 cm margin)
    • 30% metastatic rate

Staging

  • Not applicable

Report

  • Grade
  • Size
  • Margin status
  • Presence and type of heterologous differentiation

 

Lists

Biphasic lesions of the breast

Bibliography

  • Barth RJ Jr. Histologic features predict local recurrence after breast conserving therapy of phyllodes tumors. Breast Cancer Res Treat. 1999 Oct;57(3):291-5.
  • Belloq JP and Magro G. Fibroeopithelial tumours. In: Tavassoli FA, Devilee P, editors. Pathology and genetics: tumours of the breast and female genital organs. Lyon, France: IARC Press, 2003, pp. 99-103.
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