Breast malignant, males, children
Undifferentiated pleomorphic sarcoma (UPS)

Author: Emily S. Reisenbichler, M.D. (see Authors page)

Revised: 25 October 2016, last major update October 2016

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Undifferentiated pleomorphic sarcoma [title]

Cite this page: Undifferentiated pleomorphic sarcoma (UPS). website. Accessed October 26th, 2016.
Definition / General
  • See also Soft tissue topic
  • A malignant tumor showing no line of differentiation
  • Not part of the WHO classification of breast tumors
  • Previously known as malignant fibrous histiocytoma (MFH)
  • May occur as a primary / de novo tumor or in the post radiation setting
Clinical Features
  • Most occur in 5th to 6th decade of life
  • Majority present as rapidly enlarging palpable mass but can be incidental finding at screening
  • A limited core biopsy may underestimate tumor grade as grading systems such as the 3 tier French (FNCLCC) system are dependent on percentage necrosis and mitotic rate
Radiology Description
Prognostic Factors
  • Close / involved margins, large tumor size (> 5 cm) and high grade histology typically indicate a worse prognosis
Case Reports
  • Surgical resection with a negative margin (R0) is standard treatment
  • Sentinel lymph node biopsy is not warranted
  • Adjuvant radiation is often utilized in large tumors or following incomplete (R1 / R2) surgical resections
  • Response to adjuvant chemotherapy is typically low but may be used in patients with large, unresectable or metastatic tumors
Clinical Images

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Cystic tumor with skin tethering

Gross Images

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Tumor invades skin

Specimen includes ribs posteriorly

Micro Description
  • Cell morphology may be spindle, round / epithelioid or pleomorphic, demonstrating marked cytologic atypia
  • Often high mitotic activity
  • May be associated with multinucleated giant cells or an inflammatory background
Micro Images

Images hosted on PathOut server:

Courtesy of Dr. Mark R. Wick

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Marked nuclear pleomorphism and giant cells

Tumor necrosis
after neoadjuvant
Cytology Description
  • Single or clustered spindled cells with nuclear pleomorphism
  • Absence of an epithelial component
Positive Stains
Negative Stains
  • Typically negative for most markers
Molecular / Cytogenetics Description
  • Complex karyotypes without specific recurrent aberrations
Differential Diagnosis