Other malignancies
Undifferentiated pleomorphic sarcoma (UPS) / Malignant fibrous histiocytoma

Author: Kenneth Iczkowski, M.D. (see Authors page)
Editorial Board Review: Debra L. Zynger, M.D.

Revised: 21 February 2017, last major update February 2017

Copyright: (c) 2003-2017,, Inc.

PubMed Search: Undifferentiated pleomorphic sarcoma[title] or malignant fibrous histiocytoma[title]
Cite this page: Undifferentiated pleomorphic sarcoma (UPS) / MFH. website. Accessed October 17th, 2018.
Definition / general
  • Undifferentiated Pleomorphic Sarcoma (UPS, formerly called malignant fibrous histiocytoma)
    • UPS is a diagnosis of exclusion
  • UPS affects men twice as often as women and most patients are over age 50
  • Prostate is a rare site of primary tumor since most UPS are in the extremities and retroperitoneum (see Soft tissue topic)
Clinical features
  • Lung is most common site of metastasis
  • Generous sampling of tumor is needed to rule out a dedifferentiated liposarcoma, fibrosarcoma or muscle tumor
Prognostic factors
  • For UPS in general, the five year survival is around 50%
Case reports
  • Surgical excision or radiotherapy is pursued in almost all UPS cases
  • The role of chemotherapy is controversial for UPS
Microscopic (histologic) description
  • High cellularity; marked nuclear pleomorphism, frequent mitotic activity and spindle cell morphology are the hallmarks
  • High grade lesions have necrosis
  • Five histologic subtypes are described, of which storiform-pleomorphic is the most common; see Soft Tissue Chapter topic
Microscopic (histologic) images

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Malignant Fibrous Histiocytoma

Negative stains
  • To establish a UPS diagnosis, immunostains should all be negative for muscle, neural and adipose differentiation as well as a sarcomatoid carcinoma