Breast nonmalignant
Fibroepithelial neoplasms
Phyllodes tumor - malignant

Topic Completed: 1 April 2010

Revised: 9 September 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Breast [title] phyllodes malignant [title] tumor

See also: Phyllodes - generalPhyllodes - benignPhyllodes - borderline

Hind Warzecha, M.D.
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Cite this page: Nassar H. Phyllodes tumor - malignant. website. Accessed April 1st, 2020.
Definition / general
  • Phyllodes tumors with increased mitotic activity, stromal overgrowth, atypia and infiltrative borders
  • Also called high grade
  • 10% of phyllodes tumors; very rare under age 20 years
Clinical features
  • Aggressive with local recurrence, 3 - 22% metastasize to lung, bone, CNS
  • Metastases are stromal but may entrap normal epithelium
  • Death from disease is associated with recurrences and distant metastases (Am J Clin Pathol 2005;123:529)
  • Better prognosis than invasive ductal carcinoma (Am Surg 2007;73:967)
Prognostic factors
  • Poor prognostic factors: tumor necrosis, stromal elements other than fibromyxoid
Case reports
Gross images

Images hosted on other servers:

Tumors with hemorrhage and necrosis


Microscopic (histologic) description
  • > 10 mitotic figures per 10 high per fields AND stromal > ductal overgrowth (no ducts at 4x), densely packed anaplastic stromal cells and infiltrative border
  • Also tumor necrosis, heterologous stromal elements, may have cellular stroma only around blood vessels
  • Note: stroma is the malignant component and may be present in only part of the tumor so sample thoroughly
  • Stroma may resemble MFH, fibrosarcoma, liposarcoma (Am J Surg Pathol 1994;18:720), osteosarcoma (Am J Surg Pathol 1999;23:815), cartilage, skeletal muscle
  • Higher Ki67 immunostaining than benign phyllodes tumors (Mod Pathol 2001;14:185)
Microscopic (histologic) images

Scroll to see all images:

Contributed by Dr. Semir Vranić

Various images

AFIP images

Multinucleated giant cells

Squamous metaplasia and keratin cysts

Osteochondroid metaplasia

Liposarcoma component

tumor with stromal
overgrowth, atypia
and mitotic figures

Images hosted on other servers:

Squamous metaplasia and keratin cysts

Sarcomatous stroma

Pleomorphic nuclei

Infiltration into adipose tissue

Mitotic figures and abnormal mitotic figure

Multinucleated giant cells

Chondrosarcoma component

Fibrosarcomatous stroma

Liposarcoma component

MFH component

Osteosarcoma component

Rhabdomyosarcoma component

Sarcoma NOS component

Metastasis to thyroid Hürthle cell tumor



c-kit+ stromal cells and stromal giant cells

Cytology description
  • Epithelial cells, isolated spindled or round cells, phyllodes fragments, spindle cells within stroma, bipolar naked nuclei
  • Epithelial cells may overwhelm sarcomatous component (Diagn Cytopathol 2004;31:71)
Positive stains
Molecular / cytogenetics description
Differential diagnosis
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