Malignant Fibrous Histiocytoma (Pleomorphic Sarcoma) - Pathology

Introduction
A rare malignant histiocytic lesion of the bone similar in presentation to osteosarcoma, but histologically different (lacks osteoid formation) also known as undifferentiated pleomorphic sarcoma Epidemiology incidence comprises < 2% of all primary malignant bone tumors second most common bone sarcoma in adults after chondrosarcoma demographics affects individuals 20 to 80 years of age highest rates of affected patients in 2nd to 4th decades male > female (3:2) more common in Caucasians than African Americans or Asians body location 75% of cases from appendicular skeleton often metaphysis of long bones primarily distal femur, proximal tibia, proximal humerus risk factors 25% arise as secondary lesion from bone infarct, Paget disease, or prior radiation Genetics mutations of the tumor suppressor gene p53 have been implicated in tumorgenesis of secondary MFH of bone Prognosis 50% - 60% survival at 5 years worse prognosis with secondary MFH compared to primary lesions pulmonary metastasis common in up to 30% good response (> 90% tumor necrosis) to neoadjuvant chemotherapy found to have a much better prognosis age younger than 40 years associated with improved disease-free survival rate

Presentation

History
- new, painful mass
- can present with pathologic fracture

Symptoms
- pain
- constitutional symptoms
  - fevers, chills, night sweats and weight loss
Physical exam
- inspection
  - swelling
  - limp
- motion
  - decreased range of motion

Imaging

Radiographs
- recommended views
  - AP and lateral of affected area
- findings
  - lytic and destructive lesion often in the metaphysis
  - variable periosteal reaction
  - cortical destruction with soft tissue extension
  - radiographs often non-specific
MRI
- indications
  - necessary to better characterize lesion
- findings
  - deep seated heterogeneous mass
  - often associated with internal hemorrhage
  - T1- low signal
  - T2- high signal
CT scan
- indications
  - to assess the amount and character of bone destruction
Bone scan
- indications
  - may be ordered as part of pre-treatment staging
- findings
  - shows increased uptake in adjacent cortex

Studies

Labs
- elevated WBC
- eosinophilia
- abnormal LFTs
- hypoglycemia
Histology
- pleomorphic spindle cells and histiocytic cells in storiform pattern
- malignant multinucleated giant cells with grooved or indented nuclei
- areas of chronic inflammatory cells
- variable collagen production
- fibrous fascicles radiate from focal hypocellular areas
- hemorrhagic and necrotic regions not infrequent; suggest high-grade lesion

Treatment

Operative (similar to osteosarcoma)
- neoadjunctive chemotherapy, wide resection, postoperative chemotherapy +/- radiation
  - indications
    - standard of care
  - chemotherapy
    - preoperative chemotherapy given for 8-12 weeks followed by maintenance chemotherapy for 6-12 months after surgical resection
  - surgical resection
    - correct surgical option is based on the location of the tumor and the feasibility of obtaining a wide surgical margin
      - wide excision or amputation have been found to have a higher 5-year survival rate than those who received intralesional or marginal excision
    - trend towards limb salvage whenever possible
      - options include arthroplasty, resection arthrodesis, allograft reconstruction and rotationplasty
  - radiation
    - indications
      - incomplete or questionable margins in order to reduce risk of local recurrence
      - adjunct to traditional chemotherapy and surgical regimens

Differentials & Groups

	Malignant destructive lesion in older patient(1)	Sacral lesions in older patients	Treated with wide resection and chemotherapy(2)
MFH / fibrosarcoma	•	•	•
Chondrosarcoma	•	•
Dedifferentiated chondrosarcoma	•	•	•
Metastatic disease	•	•
Lymphoma	•	•
Myeloma	•	•
Secondary sarcoma	•	•	•
Osteosarcoma			•
Chordoma		•
Ewings			•
Rhabdomyosarcoma (soft tissue)			•
ASSUMPTIONS: (1) Younger patient is < 40 yrs; (2) assuming no impending fracture

IBank

	Location	Xray	Xray	CT	B. Scan	MRI	MRI	Histo(1)
Case A	humerus
Case A	femur
Case A	femur

(1) - histology does not always correspond to case

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(OBQ12.25) A 75-year-old male presents with a slowly enlarging, painless thigh mass. Physical exam demonstrates a mass measuring approximately 7 cm in size. Figure A and B demonstrate a T1-weighted MRI and T2-weighted MRI respectively. The histologic findings from a biopsy are shown in Figure C. Which of the following is the most likely diagnosis. Review Topic | Tested Concept

QID: 4385

FIGURES:

Type & Select Correct Answer

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Liposarcoma

(363/4989)

Desmoid Tumor

15%

(736/4989)

Undifferentiated Pleomorphic Sarcoma

64%

(3213/4989)

Synovial sarcoma

(388/4989)

Schwanoma

(256/4989)

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