Bone & joints

Undifferentiated small round cell sarcoma of bone and soft tissue

Undifferentiated pleomorphic sarcoma

Last author update: 1 June 2005
Last staff update: 15 September 2023 (update in progress)

Copyright: 2003-2023,, Inc.

PubMed search: malignant fibrous histiocytoma [title] bone

Nat Pernick, M.D.
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Cite this page: Pernick N Undifferentiated pleomorphic sarcoma. website. Accessed September 28th, 2023.
Definition / general
  • Mean age 34 - 40 years but all ages, no gender predominance
  • Sites: metaphysis of long bones, jaw
  • Associated with bone infarcts (30%), foreign bodies, radiation (15%), Paget disease, dedifferentiation or transformation of chondrosarcoma, chordoma or giant cell tumor (Am J Surg Pathol 1986;10:9)
  • Behaves like a high grade sarcoma with a poor prognosis, particularly for older patients and secondary sarcomas
  • Five year survival of 78% if prominent chronic inflammatory infiltrate
Radiology images

Contributed by AFIP images and Mark R. Wick, M.D.

Radiograph of tibial tumor

Primary, distal femur

Gross images

Contributed by Mark R. Wick, M.D.


Microscopic (histologic) images

Contributed by AFIP images and Mark R. Wick, M.D.

Mixture of malignant fibroblasts and histiocytes

Fibroblasts dominate

Irregular deposits of noncalcified collagen

Broad area of collagen deposits is sparsely cellular

Markedly vascular tumor

Various images

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