Bone Neoplasia and Infections

Question 1

Chondrosarcoma

Answer 1

5-10% Primary, Malignant cartilage tumour, little rings, crosses the joint, unlike osteosarcoma. Shares similar radiographic features of osteosarcomas, with histology being the only reliable means of differentiation. Main difference is chondrosarcoma are more inclined to cross a joint.

Question 2

Osteosarcoma

Answer 2

85% Primary Malignant bone tumour. Solitary metaphyseal aggressive bone lesion. Endosteal indentations/”scalloping” resulting in cortical spike formation.
Common sites for Osteosarcoma: Distal radius and proximal humerus (away from the elbow), Distal femur and proximal tibia (toward the stifle), Distal tibia, proximal femur (rare). Front limbs are affected twice as often as rear limbs.
Early to late stage Osteosacomas.
Radiographic: often moth eaten/permeative lysis pattern. Involves cortex, with palisading or spiculated sunburts periosteal reaction. Generally monostotic, and rarely crosses a joint.
DDx: Fungal osteomyelitis, multiple myelitis, lymphoma of bone, metastatic disease.

Question 3

Bone cyst

Answer 3

Fluid filled hole that develops inside a bone. Metaphyseal/diaphyseal, well demarcation of transitional zone.
When uncomplicated by fracture, the cyst contains clear serosanguinous fluid surrounded by a fibrous membranous lining. Gradually resolves on its own.

Question 4

Bone infarcts

Answer 4

Osteonecrosis in the Metaphysis or diaphysis, wavy/ocean like sclerosis, radio-opacity.

Question 5

Enchondroma

Answer 5

Trabeculae +/- radiolucent centre may be seen. DDx Bone infarcts.

Question 6

Osteoma

Answer 6

Dense cortical bone with smooth periosteal reaction. Rare. They most frequently involve the skull and facial bones and protrude from the underlying bony surface.

Question 7

Osteochondromatosis

Answer 7

Primary benign bone lesion, exostosis extending away from the cortex. Also known as multiple cartilaginous exostosis.

Question 8

Multiple myeloma

Answer 8

Malignant primary tumour, punched out, lytic appearance. Causes predominantly lucent bony changes and are accompanied by less opaque bone reaction or periosteal proliferative change. Variable findings of aggressive lysis. Generally polyostotic, either diaphyseal or metaphyseal in location.
DDx: Fungal osteomyelitis

Question 9

Osteomyelitis

Answer 9

Inflammation of bone or marrow (bacterial, fungal or haematogenous)
DDx:
- Neoplasia
- Bone cyst
- Delayed fracture union as a result of instability
- Hypertrophic osteodystrophy
- Secondary hypertrophic osteopathy
- Medullary bone infarction

Question 10

Hypertrophic Osteopathy

Answer 10

Generalised osteoproductive periosteal reaction that affects long bones of extremities. Usually caused by cardiopulmonary disease or neoplasia and may be seen with intrathoracic neoplasia. Semi aggressive periosteal new bone and cortical thickening of periosteal reaction is usually solid and lacy.