What is the WHO classification of pleomorphic sarcoma (malignant fibrous histiocytoma) of soft tissue?

Updated: Nov 07, 2018
  • Author: Gregory Scott Stacy, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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The World Health Organization (WHO) has published a classification system for tumors of the soft tissue and bone, which includes detailed cytogenetic and molecular data. Undifferentiated/unclassified sarcomas include the following subtypes [2] :

  • Undifferentiated spindle cell sarcoma
  • Undifferentiated pleomorphic sarcoma (previously classified as malignant fibrous histiocytoma)
  • Undifferentiated round cell sarcoma
  • Undifferentiated epithelioid sarcoma
  • Undifferentiated sarcoma not otherwise specified

Historically, the term malignant fibrous histiocytoma (MFH) was applied to pleomorphic spindle cell neoplasms with fibroblastic and histiocytic differentiation. However, the majority of tumors within this classification did not show any evidence of histiocytotic differentiation, and many were found to be other types of poorly differentiated tumors. The small minority of tumors for which the term MFH was most representative are now classified as undifferentiated high-grade pleomorphic sarcoma. 

Tumors are further classified by WHO as benign, intermediate, or malignant, and intermediate tumors are designated as either locally aggressive or rarely metastasizing. [2]

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