Phyllodes tumour

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Phyllodes tumour is a tumour of the intralobular breast stroma. It may be benign or malignant.

Phyllodes tumour
Diagnosis in short

Phyllodes tumour. H&E stain.

LM either (1) or (2): (1) large slit-like spaces, (2) cellular stroma - may be myxoid; +/-infiltrative border, +/-mitoses, +/-nuclear atypia, +/-"stromal overgrowth" ~ stroma fills microscopic field (see microscopic section)
Subtypes benign, borderline, malignant
LM DDx fibroadenoma, metaplastic breast carcinoma, primary breast sarcoma, other sarcomas
Gross mass with clefts - leaf-like structures
Site breast

Signs mass lesion
Prevalence uncommon
Prognosis usually benign, may be malignant
Clin. DDx other breast tumours - often fibroadenoma
Treatment wide excision

It was previously called cystosarcoma phyllodes. It is a type of fibroepithelial tumour.


  • The name comes from the word "leaf".
    • With imagination or psychotropic drugs, it may look like one: the epithelial component = the veins of the leaf.
  • Wide excision -- this differs from fibroadenoma (just local excision).
  • Approximately 6% are malignant.[1]



  • Clefts/leaf-like structures.
  • Friable - especially vis-à-vis a fibroadenoma.



Features - either 1, 2 or both of the following:

  1. Large slit-like spaces - key feature. †
  2. Cellular stroma - key feature. †
  • +/-Infiltrative border.
  • +/-Mitoses.
  • +/-Nuclear atypia.
  • +/-"Stromal overgrowth" ~ stroma fills microscopic field (see below).


  • † Large slit-like spaces are required for a benign phyllodes tumour.
    1. Slit-like spaces may absent in a borderline phyllodes or a malignant phyllodes.
    2. A cellular tumour without features suggestive of malignancy and without slit-like spaces is a cellular fibroadenoma.
      • Some pathologists don't believe in cellular fibroadenoma - they call everything with stromal cellularity a phyllodes tumour.[4]




Phyllodes tumours are graded:

  • Benign.
  • Borderline.
  • Malignant.

Grading phyllodes tumours - based on WMSP:[5]

Feature Benign phyllodes Borderline phyllodes Malignant phyllodes
Circumscription Well Well Poor
Stromal overgrowth † none none may be present
Nuclear atypia mild mild-to-moderate moderate-to-marked
Mitoses per 10 HPFs < 5 5-10 >10
Heterologous elements +/- benign +/- benign +/- malignant
DDx fibroadenoma benign phyllodes, malignant phyllodes metaplastic breast carcinoma, sarcoma


  • † Stromal overgrowth = epithelial elements absent in one low power field (LPF), defined as x40;[6] LPF is not adequately defined - see LPFitis.
  • HPF is not adequately defined - see HPFitis.

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Right Breast Mass, Excision:
- Benign phyllodes tumour.
- NEGATIVE for malignancy.


The sections show a well-circumscribed mass with a leaf-like architecture. There is no stromal overgrowth or atypia. Proliferative activity is not readily apparent.

See also


  1. Guerrero MA, Ballard BR, Grau AM (July 2003). "Malignant phyllodes tumor of the breast: review of the literature and case report of stromal overgrowth". Surg Oncol 12 (1): 27–37. PMID 12689668.
  2. Bannowsky, A.; Probst, A.; Dunker, H.; Loch, T. (2009). "Rare and challenging tumor entity: phyllodes tumor of the prostate.". J Oncol 2009: 241270. doi:10.1155/2009/241270. PMID 20069045.
  3. McCluggage, WG. (Mar 2010). "Mullerian adenosarcoma of the female genital tract.". Adv Anat Pathol 17 (2): 122-9. doi:10.1097/PAP.0b013e3181cfe732. PMID 20179434.
  4. URL: Accessed on: 23 February 2012.
  5. Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 263. ISBN 978-0781765275.
  6. Taira N, Takabatake D, Aogi K, et al (October 2007). "Phyllodes tumor of the breast: stromal overgrowth and histological classification are useful prognosis-predictive factors for local recurrence in patients with a positive surgical margin". Jpn. J. Clin. Oncol. 37 (10): 730-6. doi:10.1093/jjco/hym099. PMID 17932112.