Malignant fibrous histiocytoma

Malignant fibrous histiocytoma (MFH), which has more recently been classified as pleomorphic undifferentiated sarcoma (PUS) and formerly known as fibrosarcoma, is considered the most common type of soft tissue sarcoma. It has an aggressive biological behaviour and a poor prognosis.

As in the majority of the cases, MFH affects the extremities, this article focuses on the musculoskeletal involvement. For other rarer sites, please refer to specific articles:

Typically, MFH's occur in adults (range 32-80; mean 59 years) with a slight male predilection with an M: F ratio of 1.2:1) 3.

The presentation is usually with a painless, enlarging palpable mass.

MFH are aggressive tumours which account for 25-40% of all adult soft tissue sarcomas, making them the most common type 1. However, the classification system is becoming more restrictive, with many tumours being re-classified as variants of myogenic sarcomas 3.

They are the most frequent soft tissue sarcoma to occur as a result of radiotherapy 3 and are also seen on a background of Paget disease.

They are usually confined to the soft tissues but occasionally may arise in or from bone (1-5%) 3Although MFH can occur almost anywhere in the body, they have a predilection for extremities: lower and upper extremities corresponding to approximately 50% and 20% of the cases, respectively 2,6. MFHs of retroperitoneum represent about 16% of the cases and, those involving the peritoneal cavity, about 5% to 10% 6. Involvement of the abdominal viscera is described as extremely rare. 

Macroscopically, these tumours are typically large (5-20 cm) well circumscribed but unencapsulated with a grey firm heterogeneous cut surface sometimes with areas of necrosis 2,3.

Microscopically they are heterogeneous fibroblastic tumours made up of poorly differentiated fibroblasts, myofibroblasts, histiocyte-like cells with significant cellular pleomorphism, storiform architecture and also demonstrate bizarre multi-nucleated giant cells 2,3. They are sometimes difficult to distinguish from other high-grade sarcomas. A number of histological subtypes have been described including 2,3:

  • storiform-pleomorphic: most common 50-60%
  • myxoid: 25%, myxofibrosarcoma
  • inflammatory: 5-10%
  • giant cell: 5-10%
  • angiomatoid
    • relatively non-aggressive
    • metastases uncommon
    • usually occurs in young adults/adolescents

Plain radiographs will demonstrate a soft tissue mass and if arising from bone, then appear as an aggressive destructive bony lesion. In some cases, curvilinear or punctate regions of calcification may be demonstrated.

The density of MFH is typically similar to adjacent muscle, with heterogeneous lower density areas if haemorrhage, necrosis or myxoid material is abundant. The soft tissue component enhances. In up to 15-20% of cases, some mineralisation is present 3,4.

MRI is the modality of choice for assessing soft tissue sarcomas, as it is best able to locally stage a tumour.

These tumours are typically relatively well circumscribed, located within or adjacent to muscle, exerting a positive mass effect on surrounding structures due to their (usual) large size at presentation.

  • T1
    • intermediate (too low) signal intensity, similar to adjacent muscle 3,4
    • heterogeneity if haemorrhage, calcification, necrosis, myxoid material present
    • prominent enhancement of solid components
  • T2
    • intermediate to high signal intensity
    • heterogeneity if haemorrhage, calcification, necrosis, myxoid material present

Most MFHs are of high grade (3 and 4) and are aggressive in their biological behaviour. They frequently metastasise (30-50% at diagnosis 2) and locally recur despite aggressive treatment. The overall 5-year survival is between 25-70% 1,4.

Prognostic factors include:

  • tumour size: smaller being better
  • location
    • superficial is better
    • distal is better
  • histological grade

A tumour located superficially in the subcutaneous tissues of the distal extremity, and measuring less than 5 cm, has a 5-year survival of 80%, whereas a proximal large (>5 cm) and deep tumour has a 5-year survival of 55% 5.

Treatment usually consists of aggressive en bloc resection with a wide margin. Supplementary neoadjuvant chemotherapy and radiotherapy 4 is especially useful in reducing the local recurrence rate 5.  Limb-sparing surgery is usually possible 5.

General imaging differential considerations include:

Bone tumours

The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.

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Article information

rID: 7659
Synonyms or Alternate Spellings:
  • Malignant fibrous histiocytoma (MFH)
  • Malignant fibrous histiocytoma
  • MFH
  • Malignant histiocytoma
  • Xanthosarcoma
  • Malignant fibrous xanthoma
  • Undifferentiated pleomorphic sarcoma
  • Pleomorphic undifferentiated sarcoma
  • Pleomorphic undifferentiated sarcoma (PUS)

Cases and figures

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    Figure 1: distribution
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    Case 1: T1
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    MFH - STIR
    Case 2: STIR
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    Case 3: T1 FS + Gad
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    Case 4
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    Case 5
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    Case 6: myxoid type
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    Case 7: breast
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