Bone Tumours Flashcards
What is the term used to describe a benign tumour of osteoblasts?
Osteoma
Which familial syndrome is characterised by osteomas and large bowel polyps and is associated with an increased risk of colorectal carcinoma development?
Gardner syndrome
What is the term used to describe a benign tumour of cartilage and what does this look like on an x-ray?
Chondroma or enchondroma (if it arises within the medullary cavity). On x-ray, there is a circumscribed lucency with central irregular calcifications or a sclerotic rim and an intact cortex.
A pathologist issues the following report on a pedunculated bone tumour taken from the lower femoral metaphysis of a 20-year-old male patient. The tumour was pointing away from the knee joint. “There is a cap of hyaline cartilage which is undergoing endochondral ossification and which merges with the underlying trabecular bone. There are no atypical features”. What tumour is being described here?
An osteochondroma (exostosis).
A 25-year-old male presents with severe pain at night in his upper right thigh, which is relieved by aspirin. An x-ray shows a 1.1 cm lucency in the cortex of his right femur with a surrounding rim of reactive bone formation. Under the microscope, this shows a central nidus consisting of osteoid trabeculae separated by a vascular fibrous stroma. The nidus has a sharp margin which interfaces with a surrounding rim of mature bone. Which tumour is being described here?
This is an osteoid osteoma. Osteoblastoma is like an osteoid osteoma but is larger than 2 cm and involves the posterior components of the vertebrae and the pain does not respond to aspirin. In addition these tumours do not induce a marked bony reaction.
Which bone tumour has a soap bubble appearance on x-ray and involves the epiphysis of long bones in young adults?
Giant cell tumour of bone. This is a locally aggressive tumour of osteoclast precursors which may recur after currettage treatment. There is also a small risk (4%) of lung metastasis but these may regress and are seldom fatal.
What is the name given to a malignant tumour of osteoblasts?
Osteosarcoma.
What is the name given to a malignant tumour of chondrocytes?
Chondrosarcoma.
What is Ewing sarcoma?
A lucent tumour which involves the diaphysis of long bones in male children under the age of 15. It is a malignant proliferation of small round blue cells of neuroectodermal origin and often presents with metastatic disease but responds to chemotherapy. 5 yr survival is 65-80% for localized disease and 25-40% for metastatic disease.
What translocation characterises Ewing sarcoma?
The majority of Ewing sarcomas contain a balanced 11;22 translocation, generating in frame fusion of the EWSR-1 gene on chromosome 22 to the FLI-1 gene on chromosome 11.
What is the typical x-ray appearance of Ewing sarcoma?
They usually present as moth-eaten, permeative, destructive lucent lesions in the diaphysis of long bones, with a large soft tissue component, without osteoid matrix and they show a typical onion skin periosteal reaction. In Ewing sarcoma, the periosteum cannot produce new bone as fast as the lesion is growing. If the lesion grows unevenly in fits and starts then the periosteum may have time to lay down a thin shell of calcified new bone before the lesion takes off again on its next growth spurt. This results in a pattern of one or more concentric shells of new bone over the lesion called a lamellated or “onion-skin” periosteal reaction.
What are the risk factors for osteosarcoma?
- Familial retinoblastoma: In familial retinoblastoma there is an inheritable mutation in the retinoblastoma tumour suppressor gene which predisposes the patient to develop eye tumours called retinoblastomas as well as other tumours, including osteosarcoma.
- Paget’s disease is a disease causing an increased rate of bone turnover.
- Damage to the bone caused by infarction and radiation also increase the risk of osteosarcoma. These are referred to as secondary osteosarcomas.
How does the pathologist make the diagnosis of osteosarcoma?
Under the microscope, osteosarcomas show a proliferation of malignant osteoblasts producing osteoid.
What does an osteosarcoma look like on X-ray?
Osteosarcomas involve the metaphysis of long bones, in the region of the growth plate, often involving the knee region. Radiographs show a large destructive mixed lytic and sclerotic mass with infiltrative margins and a sunburst appearance. The tumour frequently breaks through the cortex and lifts the periosteum resulting in reactive sub-periosteal new bone formation. The triangular shadow between the cortex and raised ends of the periosteum (known radiologically as the Codman triangle) is indicative of an aggressive tumour but is not pathognomonic of osteosarcoma.
What bone lesions can show a Codman triangle?
The Codman triangle may be seen with osteosarcoma, Ewing sarcoma, osteomyelitis, aneurysmal bone cyst, giant cell tumour, metastasis, chondrosarcoma and malignant fibrous histiocytoma.
