Malignant fibrous histiocytoma

A.Prof Frank Gaillard et al.

Malignant fibrous histiocytomas (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.

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

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.

Risk factors

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.

Location

Although MFH can occur almost anywhere in the body, they have a predilection for the retroperitoneum and proximal extremities 2. They are usually confined to the soft tissues, but occasionally may arise in or from bone (1-5%) 3.

Macroscopic appearance

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.

Histology

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 sub types 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 radiograph

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

CT

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

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

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

  • T1
    • intermediate (to 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 MFH 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
Examples

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) 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
Section: Pathology
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)

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Cases and figures

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    Distribution of M...
    Figure 1: distribution
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    MFH
    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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