Histiocytoma

Definition

  • Benign fibrous histiocytoma of bone is a rare benign lesion
  • Malignant fibrous histiocytoma (MFH) is obsolete
  • MFH is now undifferentiated pleomorphic sarcoma (UPS)

Pathology

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.
  • Benign fibrous histiocytoma is histologically identical to non-ossifying fibroma (NOF)
  • Separated from NOF on clinical and radiological grounds
  • Most tumours once called MFH are other specific sarcomas on modern testing
  • UPS is a diagnosis of exclusion
  • UPS shows pleomorphic cells, bizarre multinucleated cells, atypical mitoses and necrosis

Clinical Features

  • Benign fibrous histiocytoma affects adults older than the NOF age group
  • Benign lesions are often painful, in pelvis, ribs, spine or long bone ends
  • Soft tissue UPS is among the commonest sarcomas of later adult life
  • Large, deep, painless mass in the thigh or proximal limb
  • Bone UPS is rare, affecting older adults in femur, tibia and humerus
  • Bone UPS may arise in Paget disease, bone infarcts or irradiated bone

Investigations

CT of a benign fibrous histiocytoma of the skull
CT of a benign fibrous histiocytoma of the skull. Image by Yang et Al., Wikimedia Commons, CC BY 4.0.
  • Benign lesion is well defined and lytic, often with a sclerotic rim
  • Benign lesion mimics giant cell tumour at long bone ends
  • Bone UPS is permeative or moth-eaten with cortical destruction and soft tissue mass
  • MRI for local extent, CT chest and bone scan or PET for staging
  • Biopsy at a sarcoma centre

Management

  • Curettage and grafting for benign fibrous histiocytoma, given recurrence risk
  • Wide excision with radiotherapy for soft tissue UPS
  • Chemotherapy for selected high risk patients
  • Bone UPS treated along osteosarcoma lines with chemotherapy and wide resection
  • Pathological fracture complicates local control and may lead to amputation

Prognosis

  • UPS is high grade with a risk of lung metastasis
  • Large size, deep site, positive margins and older age are adverse
  • Bone UPS fares worse than soft tissue UPS

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