Updated: 6/21/2021

Parosteal Osteosarcoma

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https://upload.orthobullets.com/topic/8015/images/Case A - posterior femur - xray - Parsons_moved.png
https://upload.orthobullets.com/topic/8015/images/Case A - posterior femur - MRI- Parsons_moved.png
https://upload.orthobullets.com/topic/8015/images/Case B - post femur - xray Ap - Parsons_moved.png
https://upload.orthobullets.com/topic/8015/images/Histology A_moved.png
https://upload.orthobullets.com/topic/8015/images/Histology C_moved.jpg
https://upload.orthobullets.com/topic/8015/images/parosteal osteosarcoma histology.jpg
  • summary
    • Parosteal Osteosarcoma is a malignant, low-grade, osteosarcoma that occurs on the surface of the metaphysis of long bones. Patients typically present between ages 30 and 40 with a painfless mass.
    • Diagnosis is made radiographically with a heavily ossified, lobulated mass arising from the cortex with biopsy showing cellular atypia seen between regularly arranged osseous trabeculae.
    • Treatment is generally wide surgical resection. 
  • Epidemiology
    • Demographics
      • more common in females, age 30-40
    • Anatomic location
      • occurs on surface of metaphysis of long bones
      • most common sites include posterior distal femur, proximal tibia, and proximal humerus
        • 80% cases occur in the femur
      • marrow invasion occurs in 25% of cases
  • Symptoms
    • Presentation
      • often presents as a painless mass
      • limited joint motion can also be a presenting complaint for characteristic large posterior distal femoral lesions
  • Imaging
    • Radiographs
      • heavily ossified, lobulated mass arising from cortex
      • appears stuck onto cortex
    • CT chest
      • mandatory staging study
      • used to evaluate for pulmonary metastasis
    • MRI
      • mandatory and must include entire involved bone
      • helps determine soft tissue/marrow involvement and skip lesions
    • Bone scan
      • mandatory imaging study
      • always hot
  • Histology
    • Characteristic histology
      • low grade lesion
      • regularly arranged normal osseous trabeculae
      • most prominent histologic feature are the atypical spindle cells seen between regularly arranged osseous trabeculae
      • some cellular atypia should be seen to make diagnosis
    • Histology can be mistaken for fibrous dysplasia
    • High rate of MDM2 amplification and ring chromosome
  • Differential
    • Fibrous dysplasia
      • similar on histology, but xrays are different
    • Myositis Ossificans Traumatica 
    • Osteochondral exostosis (shares cortex with bone)
    • Developmental defect at insertion of adductor magnus
    • Differential of Parosteal Osteosarcoma
      Bone surface lesion (cortex)
      Similar Histology
      Treated with surgery alone
      Parosteal osteosarcoma


      Periosteal osteosarcoma

      Periosteal chondroma


      Osteochondroma / MHE


      Developmental defect

      Myositis ossificans


      Chondrosarcoma

      Adamantinoma

      Chordoma
      • (controversial)
      Fibrous Dysplasia

  • Treatment
    • Operative
      • wide local surgical excision
        • indications
          • standard of care in most patients
        • technique
          • many consider geometric osteotomy of involved bone to decrease long term morbidity and retain native joint
        • chemotherapy
          • chemotherapy not indicated unless there is a high grade component
        • outcomes
          • often curative
  • Prognosis
    • 95% long term survival when local control has been achieved
      • dedifferentiation of parosteal osteosarcoma is a poor prognostic factor
      • invasion into the medullary cavity does not affect long-term survival

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(OBQ12.47) A 24-year-old male presents with increasing knee pain over the last 6 months. He reports that he sustained a non-contact twisting injury to the knee 7 months ago while playing softball. His knee range of motion is full and his knee is stable to varus and valgus at 0 and 30 degrees of knee flexion. There is a grade 1 Lachman examination. His dial test reveals 30 degrees of external rotation at 30 degrees of knee flexion. A radiograph is shown in Figure A. A biopsy is performed and is shown in Figure B. What is the most appropriate definitive management?

QID: 4407
FIGURES:
1

Reassurance and observation in 6 months with repeat knee radiographs

6%

(392/6469)

2

Neoadjuvant external beam radiation, wide surgical resection, and adjuvant chemotherapy

5%

(355/6469)

3

Wide surgical resection

47%

(3054/6469)

4

Neoadjuvant chemotherapy, wide surgical resection, adjuvant chemotherapy

37%

(2399/6469)

5

Neoadjuvant chemotherapy, marginal surgical resection, adjuvant chemotherapy

3%

(213/6469)

L 4 B

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(OBQ11.88) A 21-year-old male presents with increasing shoulder pain for the past 6 months. Radiograph, CT scan, bone scan, MRI, and histology slide are shown in Figures A through E. What is the most appropriate diagnosis?

QID: 3511
FIGURES:
1

Ewing's sarcoma

2%

(42/1925)

2

Periosteal osteosarcoma

26%

(509/1925)

3

Parosteal osteosarcoma

59%

(1132/1925)

4

Osteochondroma

7%

(138/1925)

5

Myositis ossificans

5%

(96/1925)

L 3 C

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