5. Bone tumours - overview

Question 1

Pathogenic classification of bone tumours

Answer 1

1. Osteogenic Tumours
   - Osteoma
   - Osteoblastoma
   - Osteoid osteoma
   - Osteosarcoma
2. Chondroid Tumours
   - Chondroma
   - Chondroblastoma
   - Chondromyxoid fibroma
   - Osteochondroma (exostosis)
   - Chondrosarcoma
3. Fibrogenic Tumours & Lesions
   - Fibrous dysplasia
   - Desmoplastic fibroma
   - Fibrosarcoma
4. Fibrohistiocytic Tumours
   - BFH, MFH
5. Ewing Sarcoma (Primitive Neuroectodermal Tumour)
6. Giant Cell Tumours
   - Giant cell tumour
   - Giant cell reparative granuloma
7. Miscellaneous Tumours & Lesions
   - Aneurysmal bone cyst (ABC)
   - Adamantinoma
   - Vascular tumours
8. Hematopoietic Tumours
   - Multiple myeloma
   - Langerhans histiocytosis
   - Lymphomas
9. Metastatic tumours (most common, especially in elderly)

Question 2

Epidemiology of bone tumours

Answer 2

1. Bone tumours occur at a rate approximately 1/10 of their soft tissue counterparts
2. Bimodal age population
   - First peak during 2nd decade of life
   - Second smaller peak in elderly (60 & above)
3. Bone sarcomas account only for 0.2% of all neoplasm
   - Incidence of bone sarcomas is 0.8 new cases per 100000 population per year
   - Osteosarcoma most common (35%), followed by chrondrosarcoma (25%) & Ewing sarcoma (16%)

Question 3

Precursor lesions of primary bone malignancies

Answer 3

1. High risk lesions:
   - Ollier disease & Maffuci syndrome (associated with multiple exostosis)
   - Familial retinoblastoma syndrome
   - Rothmund-Thomson syndrome
2. Moderate risk lesions:
   - Multiple osteochondroma
   - Polyostotic Paget disease
   - Radiation osteitis
3. Low risk lesions:
   - Fibrous dysplasia
   - Bone infarcts
   - Chronic osteomyelitis
   - Implants
   - Giant cell tumour
   - Osteoblastoma
   - Chondroblastoma
   - Osteogenesis imperfecta

Question 4

Staging of bone tumours

Answer 4

1. TMN Staging System
   - Size of primary tumour
   - Lymph node involvement
   - Distant metastases
   - + consideration of tumour grade
2. Enneking Staging System
   - Tumour grade
   - Anatomic location
   a. T1: One compartment (confined to bone)
   b. T2: Two compartments (tumour broken through bone into soft tissue)

Question 5

General prognostic factors for bone tumours

Answer 5

1. Size of tumours
   - <8cm better prognosis
2. Histopathological grading
3. Location of primary tumours
   - Anatomically resectable sites better prognosis
   - Spine & pelvis worse prognosis
4. Presence & site of metastases
   - No metastases better
   - If have, liver & bone mets worse than lung mets
5. Response to chemotherapy
   - >90% necrosis better prognosis
6. Specific molecular aberrations
   - Affects varying responses to chemotherapy, hence confers different prognoses