Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Malignant Fibrous Histiocytoma

Basics
Description
  • MFH is an uncommon, malignant, primary mesenchymal tumor of soft tissue or bone that resembles fibrosarcoma.
  • In primary MFH of bone, the long bones are affected most commonly.
  • Classification: Several subtypes have been described, but typing has not been shown to have prognostic implications.
General Prevention
No preventive measures are known.
 
Epidemiology
  • Individuals can be affected at any age, but the tumor mainly occurs in the 5th-7th decades.
  • No real gender predominance, although a slight male predominance may occur.
Incidence
  • An uncommon primary bone tumor:
    • The Mayo Clinic (Rochester, MN) has recorded 83 cases of MFH, representing 1% of the primary bone tumors.
  • In contrast, MFH is the most common soft-tissue sarcoma in adults.
Risk Factors
  • This tumor may arise as a complication of pre-existing bone disease (e.g., Paget disease) within a bone infarct, or from irradiation.
  • Up to 25% of cases are believed to be secondary.
Genetics
No known correlation exists.
 
Etiology
The cause is unknown.
 
Diagnosis
Signs and Symptoms
  • Identical to those of other primary bone tumors
  • Symptoms include pain and swelling, which is progressive.
  • Patients often are symptomatic for 3-6 months before diagnosis.
Physical Exam
  • The physical examination may be normal or may show only subtle findings.
  • When the tumor has penetrated the bone, a soft-tissue mass may be felt.
  • Muscle atrophy in the involved extremity is common.
Tests
Lab
The serum alkaline phosphate level may be increased secondary to bone destruction.
 
Imaging
  • Lytic bone destruction has a moth-eaten or permeative pattern.
    • Reactive bone formation may be present.
  • Large lesions may show soft-tissue extension or may be complicated by a pathologic fracture.
  • Occasionally, lesions may show focal areas of calcification.
Pathological Findings
  • Grossly, these tumors appear fibrous.
  • Light microscopy reveals spindle-cell stroma with a characteristic storiform pattern (irregularly whorled).
  • Histiocytes with slightly foamy cytoplasm and multinucleated giant cells also are prominent features.
  • Any chondroid or osteoid matrix production by the tumor cells excludes the diagnosis of MFH.
Differential Diagnosis
  • Metastatic disease
  • Myeloma
  • Lymphoma
  • Other primary mesenchymal tumors
  • Osteosarcoma
  • Fibrosarcoma
Treatment
General Measures
  • MFH typically is radioresistant, but preoperative chemotherapy may improve the surgical outcome.
  • Any patient in whom the diagnosis of MFH is suspected should be referred to a musculoskeletal oncologist for additional evaluation and treatment.
Special Therapy
Physical Therapy
Physical therapy is used extensively after limb salvage surgery or amputation.
 
Medication
Preoperative and postoperative chemotherapy are used to minimize the risk of systemic metastasis.
 
Surgery
  • In the past, amputation was the mainstay of therapy for lesions in the appendicular skeleton.
  • With recent refinements in surgical technique, limb salvage surgery with prosthetic or allograft reconstruction frequently is an option.
Follow-up
Disposition
Issues for Referral
  • Patients are monitored carefully for the development of pulmonary metastases or local recurrence.
    • Pulmonary surveillance:
      • Patients undergo serial chest CT scans every 3 months for 2 years and then every 6 months for 3 more years.
      • If metastases develop, patients are referred to a medical oncologist and thoracic surgeon.
    • Local control surveillance:
      • Patients are followed with serial radiographs, physical examinations, and sometimes CT/MRI scans (not possible in the presence of metal hardware) at 6-month intervals.
      • If local recurrence develops, patients are referred to a medical oncologist and thoracic surgeon.
Prognosis
MFH is a high-grade bone sarcoma with a >50% risk of pulmonary metastasis.
 
Complications
Recurrence and metastasis are the most feared complications.
 
Miscellaneous
Codes
ICD9-CM
171.3 Malignant fibrous histiocytoma
 
Patient Teaching
Patients with lower extremity lesions should be limited to partial weightbearing until referral to an oncologist, to avoid the possibility of pathologic fracture.
 
FAQ
Q: Do patients with MFH need surgery?
A: MFH of the bone is treated by wide resection of the bone. In addition, most patients are treated with chemotherapy.

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