Orthopaedic Tumours

Orthopaedic Tumours

·        Primary bone tumours are rare.

·        Myeloma accounts for half of malignant bone neoplasms:

o   Old, M > F, pathogenic fractures, pepper-pot skull, normocytic anaemia with Rouleaux

o   Gross: red current jelly lesions 

·        Classification based on histology of tumour cell – cell of origin is unknown/debated. Diagnosis difficult. Requires clinician, radiologist, pathologist

·        Classification:

Chondrosarcoma

·        Malignant tumour of cartilage, with no tumour osteoid or bone being formed

·        Pain becomes severe and persistent, swelling

·        Typically age 40 – 60 (average 45 years) 

·        Most common in the medullary cavity of the flat bones of the pelvis, large limb bones and ribs. Rare to involve the extremities

·        Types:

o  Conventional: eg diaphysis or metaphysis of long bones.  Margins poorly defined.  Eroded or

o   thickened cortex.  X-ray: fluffy calcification.  Grossly, pearly blue/white colour of cartilage

o  Secondary to multiple exostosis in chondrodysplasia

o  Dedifferentiated

·        Treatment: tend to metastasise late (to lung and other bones) ® attempt local excision and replacement with prosthesis

·        Prognosis: Grade 1 and 2 80 – 90% 5-year survival, Grade 3 (rare) 40% 5-year survival. Local or distant metastasis may occur up to 20 years later

Osteosarcoma (Osteogenic Sarcoma)

·        Proliferating malignant spindle-cell stroma producing osteoid

·        After multiple myeloma, it is the most common primary malignant bone tumour

·        50 – 60% of cases are near the knee (either distal femur or proximal tibia)

·        Types:

o  Conventional osteosarcoma: Most common.  Adolescent growth (age 10 – 20).  M:F = 2:1, eg

o   metaphyses of distal femur and proximal tibia. X-ray: geographic destruction, dense of lytic, raised periosteum. May also appear fibroblastic or predominantly chondroid. Gross: haemorrhagic. Micro: osteoid formation, malignant spinal cells (often see spindle cells in mesencymal tumours)

o  Second, smaller peak in 60 – 70s, secondary to existing disease (eg in < 1% of Paget‟s), previous irradiation, etc. Microscopically look like a osteosarcoma

o  Also Telangiectatic osteosarcoma, low-grade osteosarcoma, small cell osteosarcoma (like Ewing‟s but produces osteoid) and surface osteosarcomas (on the surface of the bone)

·        Investigations: X-ray, serum ALP (markedly ­), and biopsy

·        Very aggressive: assumed to have metastasised at diagnosis – usually to lung (in preference to lymph nodes)

·        Treatment: chemotherapy ® resection ® prosthesis ® post-op adjuvant chemo (high dose methotrexate)

·        5 year survival 60%

Other

·        Benign:

o  Osteochondroma: most common benign tumour of bone. Growth of an aberrant focus of cartilage on the surface of the bone (?adherent growth plate). Cartilage-capped lateral bony projection from the metaphysis, usually long bones. Also know as an exostosis. Can be hereditary (® multiple). 

o   Symptoms due to size, impingement or fracture. X-ray: mushroom like growth from metaphysis. Regular shape. If irregular then ?malignant 

o  Enchondroma: benign cartilaginous neoplasm usually arising in the medullary cavity of bone. Most common in age 20 – 50 in small bones of the hand or foot. Usually clearly circumscribed. Differential is chondrosarcoma – suspect if large bone in an older patient, erosion of the cortex or suspicious histology

o  Chondroblastoma: benign chondroid neoplasm at the end of long bones during teens

o  Osteogenic tumours: produce osteoid:

§  Osteoid osteomas: Rare. Males in teens. Exquisite pain especially at night relieved by aspirin. Well-circumscribed lesion of bony trabeculae, with variable mineralisation. < 1.5 cm. X-ray: radiolucent central zone surrounded by opaque sclerotic bone

§  Osteoblastoma: Roughly speaking, an osteoid osteoma that is > 1.5 cm

·        Fibrous dysplasia: developmental defect of bone formation ® enlargement and distortion of the bone. Feels firm, fibrous and may be gritty

·        Malignant: 

o   Ewing‟s Tumour: Rare. t(11;22)(q24;q12) usual ® fusion gene is an oncogene. Usually age 5 – 10. Usually shaft of long bones, presenting with localised pain or swelling. Small round blue cell tumour. ?neural origin. 75% 5-year survival. Can mimic osteomyelitis 

o   Giant Cell Tumour: F > M, age 20 – 40, ends of long bones, lytic lesions, contains multinucleated giant cells. Usually benign. High local recurrence, rarely metastasises

o   Fibrosarcoma

§  Malignant tumour of fibroblasts (ie collagen producing cells)

§  Occurs in any connective tissue but more common in the extremities and middle aged

§  Fibrosarcoma of the bone is rare.  Swelling, pain, pathological fracture

o   Synoviosarcoma:

§  Rare malignant tumour of the synovium, usually sharply circumscribed

§  Rapid enlargement of the joint with pain.  Usually knee, hip or shoulder

§  May extend along fascial lines and invade bone

§  Treatment: if small then excise, if high grade: resection + radiotherapy + chemotherapy

Secondary Bone Cancer

·        Most common bone cancer Þ always ask about previous primaries

·        Source: breast > prostate > kidney > lung > thyroid

·        Sites: vertebrae, pelvis, proximal femur, humerus

·        Spread: usually haematogenous.  Occasionally local extension

·        Usually osteolytic ® pathological fractures

·        Presentation:

o   Pain + history of cancer in 50 – 70 year old

o   In children < 6 years: from neuroblastoma

o   Symptoms of hypercalcaemia: anorexia, nausea, weakness, depression, polyuria

·        Investigations:

o   Xray: usually osteolytic lesions (if osteoblastic probably carcinoma)

o   Bone scan, FBC, ALP, Electrophoresis (myeloma)

o   FNA: determining cell of origin helps guide management 

·        Treatment: usually palliative, control pain, prophylactic fixation, spinal stabilisation, radiotherapy (¯ pain)