Malignant Fibrous Histiocytoma

Definition

  • Primary malignant neoplasm of bone & or soft tissue which contains fibrous & histiocytic elements

Epidemiology

  • Rare
  • 1 per million or one per 2 million
  • Affects older age group 40-70
  • More common in males

Site

  • Metaphysis of long bones, more so lower limbs than upper limbs

Aetiology

Pathology

Malignant Fibrous Histiocytoma, histology of undifferentiated pleomorphic sarcoma, formerly called malignant fibrous histiocytoma
Histology of undifferentiated pleomorphic sarcoma, formerly called malignant fibrous histiocytoma. Image by Nephron, Wikimedia Commons, CC BY-SA 3.0.
  • “storiform pattern”
    • there is an appearance of wheel spokes radiating from a slit like vessel, in a fibrous background
    • A storiform pattern is not however diagnostic of MFH because it is also seen in osteosarcomas, leiomyosarcomas, neurogenic sarcomas, haemangiopericytomas & non ossifying fibromas
  • Other typical histological features are bizarre histiocytic cells, numerous mitotic figures, & scattering of chronic inflammatory cells

Histological variants:

  1. MFH – myxoid subtype
    1. Sheets of myxomatous tissue with large histiocytes & abnormal mitoses
  2. MFH – Inflammatory subtype
    1. Field of malignant histiocytes peppered with acute inflammatory cells, which may obscure the fibrous elements
  3. MFH – Giant cell type
    1. Large number of multinucleated giant cells
  • Stout’s hypothesis – theory of histiocytic & fibrous origin: histiocytes are derived from bone marrow monocytes – “tissue macrophages”. Histiocytes have the potential to transform to spindle cells which produce collagen, & are indistinguishable from fibrocytes
  • MFH is a diagnosis of exclusion; if the tumour resembles MFH but produces regions resembling another malignant tumour it is diagnosed as that tumour

Clinical

  • Pain, swelling, pathological fracture
  • Relatively high metastatic potential, usually to lungs & other bones

Investigations

Laboratory

No characteristic alterations

X-ray

  • Lesions usually lytic or permeative; may expand cortex without breaching it
  • Frequent periosteal reaction
  • High index of suspicion if permeative radiolucency adjacent to bone infarct, fibrous dysplasia or Paget’s disease

MRI

  • T1 – low or intermediate intensity
  • T2 – high intensity

Immunohistochemistry

  • Vimentin stain positive
  • More specific is A1-AT antibody which also binds normal histiocytes

Treatment

  • Induction chemotherapy
  • Limb sparing surgery

Prognosis

  • Poor – around 60% 5ysr, but probably has a better prognosis than other sarcomatous lesions
  • Prognosis worse for secondary lesions. 40% alive at 4 years

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.